I have one Sim who is an author and she has mastered gardening. She earns a lot of her money on gardening, she paints once in a while and writes her books. She has about 149,000.
The other Sims have jobs and I had to give them money.
One of my painter Sims sells paintings on plopsy but he just started that and they all have the bee box, selling the honey.
Both the Astronaut and Tech Guru also sell statues and other things made with the handy woodworking.
I agree with @haneul its the side jobs that make the money.
