Unlimited hit points
Get access to fourth level Vine magic, and learn the spell Toughen. Leave the town and cast it on the desired character. Cast it as many times as you have the Mana to do so. Next, re-enter the town. Note that the Toughen symbol on the character's portrait is gone, yet the extra hit points remain. Leave the town again. You will have full Mana, and can repeat the trick again until you get 999 HP, even with a Warlock or Wizard.
You can create up to 18 characters at the beginning, and each will start with 200 gold. Make those characters and add them to your party. Then, take their money and delete the characters. If you have the time and patience, you can get as much gold as needed.
Go to Ishad N' ha and go to the pawn shop. Induct your rouge into the Thieves Guild, then accept the Dragon Arrow quest. Find Torin (in the Shire) and give him the arrow. Then, go back to the pawn shop and collect 1000 experience for completing the quest. After this is done. go back to where Torin was and steal from him until you get the Dragon Arrow. Go to the pawn shop and sell the arrow for 1600 gold. You will be able to buy it back for only 200 gold. Repeat this as many times as needed.
Create two characters in the inn. Put them both into your party. Then, exit the inn, and give as much gold as you would like to the second character in your party. Re-enter the inn, and remove only the second character (the one with the gold.) Then, add them again to your party. Have your first character (that was not removed from the party) pool all of the gold. Once again, remove the second character from your party. Add the second character again, and have the first member of the party pool the gold again. Repeat this as needed. Each time you add, pool, and remove the second character, your first character should receive as much gold every time as you had originally given your second character outside the inn. For example, while outside the Inn, you give the second character 1,000 gold pieces. Once you re-enter the inn, and remove the character then add him/her back into the party and pool your gold, you should receive 1,000 gold every time. Note: You must give the gold to your second character outside the inn, then re-enter, or you may lose all of the gold on the removed characters. You can also leave town, then pool the gold to a character, save the game (just to be safe to ensure to prevent any loss of gold), then return to the inn. Then, do the remove, add, pool, remove parts of the trick.
Join the Fighter's Guild, buy a magic arrow or bolt. then sell it. The cost of buying magic arrows and bolts is much cheaper then the prize you sell it for. This gap gets even greater when joining the Dojo and buying a magic arrow there. You can buy for 250 gold and sell for over 1000 gold.