As a thief, your income will come from whatever you can get your greedy mitts on.
You can use an iron hoe, golden hoe or a diamond hoe to pick locks and steal whatever goodies you can find.
Each will last longer/have a higher pick chance.
You can also make money by chartering your services. People will pay for you to empty any chests in towns (as moderators will only remove the locks on empty chests)
- Iron+ Hoes (but not for farming)