Assuming you have Marina unlocked then ask her for office work in the morning. Otherwise hope you like washing dishes at home. As far as I know those are the only two ways to grind money.
Also don't forget about vacuuming the livingroom, it also gives you money.
Wasn't sure about that one. Laundry doesn't give any money after the first time and assumed nothing else did until I washed dishes again by accident.
