Hi, Johnlewis82,
First of all, let me say I work at a car auction where we put through 3,500 to 5,000 cars per week & some of the dealers who buy cars there won't touch an ex-rental but others have no problem with them. The general consensus is that rental cars get abused by some of the renters (I don't think they get any more abuse than some lease cars). I personally treat any car I rent just as though it were my own & I wanted it to last forever, but I have met some people who just rent cars when they want something to beat up on a cross-country trip & not put the wear & tear on their own car. There may be some risk as far as the type of use/abuse by some renters, but the maintenance given the rentals is quite rigidly adhered to, so they should be in good condition as far as that goes. It used to be that you could get the car's maintenance records when you bought an ex-rental, but now because of privacy laws they may show them to you briefly but not let you have them.
A lot of rental companies turn in large batches of cars at a time to car auction places like the one I work at, but some companies like Enterprise have their own lots where the general public can go to look & browse, test drive, & buy & drive off the lot with a car on the same day. You may not be so lucky to have such a lot close by, but some of the other rental companies also have have internet listings of their cars for everyday sale (or even special sales at special locations) & if you so desire to buy with them online, they can even ship the car to one of their local lots or agencies for a fee. As for pricing at one of these rental locations, I think the ex-rental cars will list for about the same price as any fairly priced used car on a dealer's lot & you may still be able to negotiate. I also think that Enterprise (at least) gives you a better used car warranty than you get from a regular used car dealer's lot (but the rental companies can't sell you an extended warranty---you can still get that directly from Toyota if the car is less than 3 years old & has less than 36,000 miles on it). My credit union has worked out a deal that if you buy from the Enterprise lot & finance through the credit union, the credit union makes a $500 deposit into your credit union savings account.
I just couldn't get my Prius that way 5 years ago because Toyota mandated that all Priuses be returned to Toyota for auction back to their own dealers because of the high demand for the Prius back then. I understand that things have changed since then & Enterprise sales agents will even work with you to get you (or identify/claim/reserve for you a specific car when it becomes available for sale) the car you want (I doubt all the option pkgs Toyota offers will be available in the rental fleet) as far as color combinations & mileage.