If you do buy the car, make sure you get it checked by a mechanic first. Check the vehicle history report. Make sure it doesn't have too many miles. Look at consumer reports for that make and model on edmunds. Make sure all the seat belts, doors, and locks work. If something is wrong, it presents an opportunity to haggle on the price.
At any rate, you can get a guard card for like $300 and make about the same you'd make driving for Uber/Lyft. If i were you, I would focus on growing that online thing you got. Maybe reinvest money into that.