I found that gaining money in the vanilla game to be a little bit too
much of a chore, but other economy mods I have tried made making money
so easy it lost any challenge at all.
Finally I went into the files and created my own economy mod. This mod
slightly edits the economy so that both you and your drivers earn a
little more money. Additionally you get 25% fuel discount at your own
garages instead of 15%.
The changes are minor so that it still takes a while to gain cash, but
it is a little easier.
Built from scratch to work with the 1.9 patch. Also works with