I tried flippin cars once. I found that getting good cars was something that you just happen upon by coincidence. When I actively looked, I never found a good car to flip. The few that I did find, I stumbled across while not even looking for one. Even then, you have to talk them well below value. Then, on the sale you have to do the opposite and talk it up out of somebody's pocket. Not to mention you have to convince the seller to not fill out specific title info. Then you try and just pass the title over to a buyer without even transferring it into your name first. The only way to make money doing this is to be a shady character.
It's not legal and not a good feeling in the end.