So reading the responses everyone who has bought a former rental car has positive things to say, and those who have never done it are the ones saying don't do it.
er...except for the person who posted bright above you.
LOL glad you saw that!!
My family bought 3 rental cars over the course of 10 years. Transmission leak issues, sudden broken drive belts, weird suspension issues, exhaust issues, odd engine idle issues, you name it, we've experienced it over the course of 3 purchased rental cars.
Most people treat rental cars like trash. They'll start it up and drive it down the block, without warming up the engine at all. They'll drive rental cars off-road, they'll do all kinds of stuff you'd never do to your own car. I shudder to think of the crap people do in the inside of rental cars on top of that (including various kinds of unmentionable fluids, literally dog crap when they bring their dogs, etc, and then wipe off before returning them).
We will never touch or buy a rental car ever again. I'm glad others are far luckier, but it's truly a huge risk to buy a rental car, imho.