Get your Guile skill to the maximum and find a store that has a lot of jewels for sale (diamonds, rubies, jets, and sapphires), such as the the store at Hook Coast. The more they have, the more money you can get. With the Guile skill maxed, you can buy cheaply and sell them back to the same store for more money.
Go to the Darkwood Bordello. You will find the passage to Darkwood Bordello in Darkwood Lake. You will meet Madame Minzche, who will tell you about how she wants the deeds to the place. Get a dress and put it on, then get a red wig; there is one in the bedroom. When you have your outfit on, talk to the owner who will think you are a lady. He will take you to the bedroom. You will get 1,000 gold each time you sleep with him. Note: You cannot have any facial hair when doing this.
Go to the Darkwood Camp area and save the game. Then, go to the blackjack dealer in the camp and place your maximum bet. If you lose, load your game and try again until you win. After winning, overwrite your last save and repeat the trick. The game is fixed for you to lose most of the time, but do not give up; eventually you will win.
Buy the house in Oakvale which you used to live in when you where a child. Put some trophies in there for decoration, then sell the house for more money than you bought it. Break down the door, take the trophies and buy it for less than you sold it for previously. Repeat this process as much as desired to make easy money.
Note: A high level Guile (level 3 to maximum recommended) is needed in order to get the most out of this trick. Once you are a well recognized Hero, have a decent amount of gold, and some good stats, you can steal from general shops throughout Albion and re-sell the items (if there are some empty spaces on the store display). Then, steal the item, sell it, etc. If you get caught, use your "Apologize" expression. Some good items are gems and wedding rings. If you are trying to get gems or a wedding ring, you should steal from the Oakvale general store (the one that has a sign of a bag which looks like your coin purse).