well being 72% done i would have to say one thing first find all hidden packages that is 100k when you do buy the mailbu clup you really dont need to look for money for a while but here are the income of places in the game

Sunshines Auto: starts at 1,500 for deliever the first set of cars then by the time you deliever the final cars you will have a income of 9,000
Vercittets place:5,000
Print Works:7,000
that is all i can remember of the top off my head