Here is a stolen job guide [I'm a pirate at heart] 

Once you have had an intermediate or advanced job from a quest. If you change jobs, you will be able to go back to that job. The Fee for a previous job is somewhat steep, ranging from 1.4mil to 4.8mil to 100mil and possibly beyond.  

Job switch guide with quest locations
  0.0 | by Norton on Oct 09, 2011 07:34 PM

You can switch your main 3 classes using a 'Guild change card' obtained from doing school or the beginner job quests. More details available here. (this guide is similar) Talk to the GM npc in the quest guild houses in-game of any major city.
You can safely switch jobs or class anytime without losing any of your skills or their obtained proficiency.
There is no need to use the cash shop although guild cards sold there can save you time, all you are advised to do is re-equip your toon with the appropriate clothes, armour, weapons or items.
All jobs have favoured skills, many have expert skill bonuses as stated on the main UWO web-site guide.
Later on, upon reaching the required lvl or pre-requisites you can specialize in an intermediate or more advanced master job obtained by doing a quest/s from the list below:

Adventure Beginner Jobs

  • Adventurer Learner 
    Total LV :1 / Adventure 1 / Trade 0 / Battle 0 City: Character Creation
  • Explorer / Surveyor / Biologist / Fisher 
    Total LV: 2 / Adventure 2 / Trade 0 / Battle 0
    City 1: Any Main city (5star)
    Quest 1: Adventurer guild's plight
    Skills 1: Sail Handling 1
    City 2: Lisbon (4star)
    Quest 2:Rumours of a Mask from Cueta
    Skills2 : Sail Handling 1
  • Excavator 
    Total LV: 7 / Adventure 4 / Trade 0 / Battle 0
    City 1: Any Main city (5star)
    Quest 1: Adventurer guild's plight
    Skills 1: Sail Handling 1
    City 2: Lisbon (4star)
    Quest 2:Rumours of a Mask from Cueta
    Skills2 : Sail Handling 1
  • Helmsperson 
    Total LV: 5 / Adventure 4 / Trade 0 / Battle 0
    City 1: Any Main city (5star)
    Quest 1: Adventurer guild's plight
    Skills 1: Sail Handling 1
    City 2: Lisbon (4star)
    Quest 2:Rumours of a Mask from Cueta
    Skills2 : Sail Handling 1

Adventure Intermediate Jobs
  • Historian
    Total LV :24 / Adventure 15 / Trade 0 / Battle 0
    City: Tunisia / Istanbul (5 star)
    Quest: Treasure of Ilkhanate
    Skills: Search 1, Archaeology 3, Unlock 1
    Other: Adventure fame 2000
  • Missionary
    Total LV :24 / Adventure 15 / Trade 0 / Battle 0
    City: Venice (5 star)
    Quest: Statue of Madonna and child
    Skills: Search 2, art 4, German
    Other: Adventure fame 1800
  • Cartographer
    Total LV :36 / Adventure 20 / Trade 0 / Battle 0
    City: London (6 star)
    Quest: Investigation of Mercator
    Skills: Recognition 4, Geography 11, Dutch
    Other: Adventure fame 5000
    Prequest City: London / Lisbon / Seville / Marseille (6 star)
    Prequest Name: Coral Sea
    Prequest Skills: Recognition 4, Geography 6
  • Hunter
    Total LV :36 / Adventure 20 / Trade 0 / Battle 9
    City: Istanbul (9 star)
    Quest: Request from a master
    Skills: Ecological Research 11, Biology 11, Arabic
    Prequest City: Amsterdam / Seville / Marseille / Tunis (9 star)
    Prequest Name: Hydrophobic Hippo
    Prequest Skills: Ecological Research 9, Biology 11, Portugeuse
Adventure Master Jobs
  • Treasure Hunter
    Total LV :42 / Adventure 20 / Trade 8 / Battle 0
    City: Tunisia, Istanbul (5 star)
    Quest: Treasure of Ilkhanate
    Skills: Search 1, Archaeology 3, Unlock 1
    Other: Adventure fame 2000
  • Ocean Explorer
    Total LV :45 / Adventure 25 / Trade 0 / Battle 0
    City: Seville (9 star)
    Quest: Speed challenge
    Skills: Sail Handling 6, Spanish
    Other: Adventure fame 5500
  • Archaeologist
    Total LV :45 / Adventure 25 / Trade 0 / Battle 0
    City: Athens / Alexandria / Istanbul (8 star)
    Quest: Treasure of the kings of Troy
    Skills: Search 8, Archaeology 10, Greek
    Other: Adventure fame 9000
    Prequest City: Marseille (8 star)
    Prequest Name: 
    Prequest Skills: Recognition 8, Archaeology 10, Theology 4
  • Thief
    Total LV :50 / Adventure 20 / Trade 15 / Battle 15
    City: London (9 star)
    Quest: The knights of the hundred year war
    Skills: Search 9, Archaeology 9, English
    Other: Adventure Fame 6000
  • Priest
    Total LV :50 / Adventure 28 / Trade 0 / Battle 0
    City: Venice (5 star)
    Quest: Statue of Madonna and child
    Skills: Search 2, Art 4, German
    Other: Adventure fame 1800
  • Naturalist
    Total LV :50 / Adventure 28 / Trade 0 / Battle 0
    City: Venice (6 star)
    Quest: Natural history treatise
    Skills: Biology 12, Italian
    Other: Adventure Fame 11000
    Prequest City: Cape Town (9 star)
    Prequest Name: Monster Bones
    Prequest Skills: Search 10, Biology 12 Spanish
  • Guerilla
    Total LV :65 / Adventure 28 / Trade 0 / Battle 24
    City:Venice (6 star)
    Quest:The nation's treasure
    Skills:Italian, Throwing 8
    Prequest City: Marsielle/Genoa/Venice (3 star)
    Prequest Name: Roman ruins buried
    Prequest Skills: Recognition 1, Archeology 1, Italian
  • Interpreter
    Total LV :65 / Adventure 28 / Trade 20 / Battle 0
    City: Amsterdam (8 star)
    Quest: To relay the will of the forefathers
    Skills: Latin, Hebrew, Ancient Egyptian
    Prequest City: Amsterdam (6 star)
    Prequest Name: The production version
    Prequest Skills: German, Dutch, Kaer Te Language
  • Folklorist
    Total LV :65 / Adventure 35 / Trade 0 / Battle 20
    City: Athens (7 star)
    Quest: The new research of the scholar
    Skills: Geography 7, West Africa Language
  • Salvager
    Total LV :80 / Adventure 38 / Trade 10 / Battle 10
    City: Athens (3 star)
    Quest: Daily-advancing technologies
    Skills: Salvage 5, Greek
  • Ranger
    Total LV :108 / Adventure 52 / Trade 0 / Battle 22
    City 1: Aden (10star)
    Quest 1: A long journey to link dreams
    Skills 1: Eco 13, Bio 15, Indian
    City 2: Calicut (10 star)
    Quest 2: Honour of an adventurer
    Skills 2: Eco 13, Bio 15, Swordplay 7
  • Artist
    Total LV :116 / Adventure 48 / Trade 0 / Battle 0
    City 1: Naples (9 star)
    Quest 1: Restoration of famous items
    Skills 1: Search 11, Art 13, Handicraft 8
    City 2: Naples (9 star)
    Quest 2: Revival of the Trojan war
    Skills 2: Italian, Handicraft 8
  • Adventure Mentor
    Total LV :60 / Adventure 32 / Trade 5 / Battle 5
    City: Genoa (5 star)
    Quest: Outline of adventure course teaching
    Skills: 
    Other:
  • Ruins Explorer
    Total LV :76 / Adventure 32 / Trade 0 / Battle 20
    City: Tunisia (8 star)
    Quest: An obstruction in the way
    Skills: Trap 5, Archaeology 5, Arabic
    Other: Adventure fame 5000, Maritime 30000??
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
Merchant Beginner Jobs
  • Trade Learner
    Total LV :Total LV.1 / Adventure 0 / Trade 1 / Battle 0 City: Character Creation
  • Foods Dealer / Yarn Dealer
    Total LV: 2 / Adventure 0 / Trade 2 / Battle 0
    City : Any Main city (5star)
    Quest : Merchant guild's plight
    Skills : Sail Handling 1
  • Accountant / Chandler / Mineral Trader / Medicine Trader / Animal Trader
    Total LV: Total LV.4 / Adventure 0 / Trade 3 / Battle 0
    City : Any Main city (5star)
    Quest : Merchant guild's plight
    Skills : Sail Handling 1

Merchant Intermediate Jobs
  • Chef
    Total LV :36 / Adventure 10 / Trade 20 / Battle 0
    City: Stockholm (5 star)
    Quest: Procure food for soldiers
    Skills: Nordic, Cooking 5
    Other: Trade fame 3000
  • Trading Merchant
    Total LV :36 / Adventure 0 / Trade 20 / Battle 0
    City: Marsielle (6 star)
    Quest: Procure food for the navy
    Skills: French, Cooking 12
    Other:
Merchant Master Jobs
  • Art Dealer 
    Total LV :45 / Adventure 0 / Trade 25 / Battle 0
    City: Santo Domingo (9 star)
    Quest: Crafts from the New World
    Skills: English, Art Trading 5, Craft Trading 5
    Other: Trade fame 9000
  • Money Trader 
    Total LV :50 / Adventure 0 / Trade 28 / Battle 0
    City: Santo Domingo (9 star)
    Quest: Silver from the New World
    Skills: Metal Trading 5
    Other: Trade fame 9000
  • Jeweller
    Total LV :50 / Adventure 0 / Trade 28 / Battle 0
    City: Calicut (8 star)
    Quest: Sapphires to Europe
    Skills: Portuguese, Jewellery Trading 5
    Other:
  • Arms Dealer
    Total LV :50 / Adventure 0 / Trade 28 / Battle 16
    City: Marsielle (3 star)
    Quest: Da Vinci's research
    Skills: French, Casting 5
    Other: Maritime Fame 5000
  • Spice Trader 
    Total LV :50 / Adventure 0 / Trade 28 / Battle 0
    City: Calicut (8 star)
    Quest: Spices to Europe
    Skills: Spice Trading 5
    Other: Trade fame 9000
  • Patissier
    Total LV :116 / Adventure 0 / Trade 48 / Battle 0
    City: Lisbon (7 star)
    Quest: Carlotta makes up her mind, The famous patissier
    Skills: cooking 12
    Other: pre quest named something like The lovely pastry
  • Tailor
    Total LV :100 / Adventure 0 / Trade 48 / Battle 0
    City: Marsielle (8 star) / Marsielle (7 star)
    Quest: Dream of the noblewomen / Royal Warrant Craftsman
    Skills: Sewing 13, French, Italian, / French Sewing 13
    Other: Trade fame 50000
  • Blacksmith
    Total LV :100 / Adventure 0 / Trade 48 / Battle 0
    City: London (8 star)
    Quest: A message
    Skills: English, Casting 13
    Other: Trade fame 50000
  • Artisan
    Total LV :100 / Adventure 0 / Trade 48 / Battle 0
    City: Venice (7 star)
    Quest: Founding ceremony
    Skills: 7 sewing, 7 casting, Greek
    Other: Adventure/Trade fame 50000
  • Alchemist 
    Total LV :116 / Adventure 32 / Trade 46 / Battle 0
    City: Alexander (6 star) / Alexander (6 star)
    Quest: Fostering the art of alchemy / Learning from Paracelsus
    Skills: both Italian, handicraft 13
    Other:
  • Sommelier
    Total LV :80 / Adventure 10 / Trade 41 / Battle 0
    City: Marsielle (4 star)
    Quest: The depths of the wines of the world / Daily-advancing technologies
    Skills: Alcohol Trading 8, French, Dutch
    Other:
  • Artificer
    Total LV :116 / Adventure 32 / Trade 54 / Battle 0
    City: Venice (8 star)
    Quest: The chance to show the skill
    Skills: 
    Other: pre quest name something like Proprietress of the mind 8 star Venice
  • Political Merchant
    Total LV :80 / Adventure 10 / Trade 35 / Battle 18
    City: Seville (8 star)
    Quest: Bargain and trade
    Skills: Metal Trading 7, Socialbilty 7, Arabic
    Other:
  • Caravanner
    Total LV :116 / Adventure 32 / Trade 38 / Battle 32
    City: Alexandria (8 star)
    Quest: Caravan's instinct
    Skills: Livestock trading 7, Search 7
    Other: Adventre Fame 10000, Trade fame 50000, Battle fame 10000
  • Merchant Mentor 
    Total LV :60 / Adventure 5 / Trade 32 / Battle 5
    City: Genoa (7 star)
    Quest: 
    Skills: Italian social 5 (business courses have graduated, without hanging the title) ??
    Other:
  • Master Alchemist
    Total LV :120 / Adventure 36 / Trade 50 / Battle 0
    City: Venice (7 star)
    Quest: Advanced alchemist's title
    Skills: Alchemy 10, Casting 10, English
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Maritime Beginner Jobs
  • Maritime Learner
    Total LV :Total LV.1 / Adventure 0 / Trade 0 / Battle 1 City: Character Creation
  • Mercenary / Bodyguard
    Total LV :2 / Adventure 0 / Trade 0 / Battle 2
    City: Any Starting City / Genoa /Athens
    Quest: Intercept the Privateer fleet
    Skills: Ballistics 1
  • Brigand
    Total LV :4 / Adventure 0 / Trade 0 / Battle 3
    City: Any Starting City / Genoa /Athens
    Quest: Intercept the Privateer fleet
    Skills: Ballistics 1
  • Jr. Officer
    Total LV :7 / Adventure 0 / Trade 0 / Battle 4
    City: Any Starting City / Genoa /Athens
    Quest: Intercept the Privateer fleet
    Skills: Ballistics 1

Maritime Intermediate Jobs
  • Naval Officer
    Total LV :24 / Adventure 0 / Trade 0 / Battle 15
    City: Athens (7star) / Amsterdam,London (7star)
    Quest: Diokytes / Zealand Plunderer Fleet
    Skills: Greek, Ballistics 5 / Nordic Ballistics 5
  • Privateer
    Total LV :24 / Adventure 0 / Trade 0 / Battle 15
    City: Alexandria, Tunisia , Cyprus, London (7 star)
    Quest: Privateering order
    Skills: Portuguese, Swordmanship 5, plunder 3
  • Bounty Hunter
    Total LV :36 / Adventure 10 / Trade 0 / Battle 20
    City: Seville (10 star)
    Quest: The golden stag
    Skills: Spanish, Evasion 4
    Other: maritime fame 4000
  • Surgeon
    Total LV :36 / Adventure 0 / Trade 10 / Battle 20
    City: Seville (3 star)
    Quest: The medical theory
    Skills: Surgery 4, Spanish, Italian

Maritime Master Jobs
  • Shipwright
    Total LV :42 / Adventure 18 / Trade 9 / Battle 9
    City: Lisbon (3 star)
    Quest: Latest tactics
    Skills: Tactics 7, Spanish, English
    Other: Maritime Fame 6000
  • Senior Officer
    Total LV :50 / Adventure 0 / Trade 0 / Battle 28
    City: London, Amsterdam (9 star) / Athens (9 star)
    Quest: Bacilias / Counterattack on the Baltic pirates
    Skills: Nordic, gunnery 5
    Other:
  • Tactician
    Total LV :50 / Adventure 0 / Trade 0 / Battle 28
    City: Lisbon (3 star)
    Quest: Latest tactics
    Skills: Tactics 7, Spanish, English
    Other: Maritime fame 6000
  • Cannoneer
    Total LV :50 / Adventure 0 / Trade 0 / Battle 28
    City: Marsielle (3 star)
    Quest: Co-writing with the technician
    Skills: Ballistics 5, French
    Other: Maritime 6000
  • Pirate
    Total LV :50 / Adventure 0 / Trade 0 / Battle 28
    City: Amsterdam 7 star
    Quest: The councillor's request
    Skills: Dutch, Swordmanship 10, Plunder 6
    Other:
  • Swordfighter
    Total LV :50 / Adventure 0 / Trade 0 / Battle 28
    City: Calicut (8 star)
    Quest: Fierce warriors of Mohenjo-Daro
    Skills: Swordmanship 12, Assault 6
    Other: Maritime fame 4000
  • Scout
    Total LV :116 / Adventure 22 / Trade 0 / Battle 48
    City: Seville (10 star)
    Quest: The first step to defeating pirates
    Skills: Spanish, evasion 14
    Other:
  • Supply Corps
    Total LV :80 / Adventure 0 / Trade 16 / Battle 36
    City: Lisbon (8 star)
    Quest: The courier who got involved
    Skills: Arabic, Repair 11
    Other:
  • Sword Master
    Total LV :65 / Adventure 0 / Trade 0 / Battle 36
    City: London (6 star)
    Quest: The pride of the Swordfighter
    Skills: English, Swordmanship 8
    Other:
  • Musketeer
    Total LV :65 / Adventure 0 / Trade 25 / Battle 27
    City: Marsielle (star 6)
    Quest: Summons from musketeers
    Skills: French, Italian, Gunfire 8
    Other:
  • Filibuster
    Total LV :104 / Adventure 25 / Trade 25 / Battle 54
    City: Santo Domingo (10 star)
    Quest: The pirates known as 'Fear', Devil's progeny, Fear's call
    Skills: 
    Other: Notorious 3000
  • Guardian
    Total LV :80 / Adventure 0 / Trade 10 / Battle 41
    City: Seville 3 star
    Quest: The life saving corps
    Skills: surgery 5, lookout 3
    Other: Maritime fame15000
  • Maritime Mentor
    Total LV :60 / Adventure 5 / Trade 5 / Battle 32
    City: Genoa 7 star
    Quest: Outline of adventure course teaching
    Skills: Socialbility 5, Italian


When you feel you have become good in any of the above jobs come back here and write a guide.
Thank you, don't get bored, switch jobs and have fun!