The best way to gain money is ilegally but legally is saffer...


Choose your side!

Choose any character. If you're going ilegally it's often better to use a thief and any other if you like to be a safe, legal money gainer:

-LEGAL
It's often better to tailor. Raise your tailor skill with a tinker, but don't forget to save some money to buy some yards of sheets, a sewing kit, scissors and yarns... Use the sewing kit first, then the scissors and the rest as you intend.

Sell it to a clothes shop or something.

Write a book. That's what books are for. Then, sell to scribes.
Buy some scrolls, potions, runes and sell it. It often gives you money.
Fight. Sell the bones, and the entrails of the animal/beast and get some money!
There are more, but I'll let you to find out... :-)

-ILEGALLY
The way to get the most money is to steal books from libraries and sell it to scribes. You'll get 6-7gps per book, so it's a
good deal.
Find some PC and drag him/her to a place where you leave the protection of Lord British's guards, then, KILL HIM/HER!!!

But look out! Although you can steal from him/her's dead body, he/she may report you to the guards, so stay on the look out!
I found this nifty bug (or is it not?): find a place with rooms and NPCs. Find an NPC near a room. Try to steal an object with little or no value. Log off before you get killed. Log on.

When it gives you the chance of becoming a ghost or the penalties, choose the panalties... TA-DAAAAA!! The NPC's backpak is in the room and ready for the taking!
There are more, but, like in above, you must find out!