Back in my college days I used to work for enterprise as a lot jock on nights. As others have said, rental companies are good about keeping maintenance in check. That said, there ARE some caveats I can share...
1. Because cars change locations so frequently and enterprise is nationwide, they contract out the maintenance work to shops local to each rental office. Enterprise "shops around" and typically provides the contract to the cheapest (but legit) garage in town. So that said, the maintenance is never performed at a dealership. While this is positive in that it supports local small businesses, it does mean that any maintenance done wasn't done at the dealer. (Excluding warranty work, vehicles are always brought to dealers for that)
2. Major things like transmissions and AC are checked before a rental is deemed ok to sell. If anything goes wrong with big components after a sale, the rental companies are usually good about covering those expenses. It's the small things you have to specifically look for and point out before you buy, as most rental companies won't cover things like broken buttons, dead backlighting, minor electronics issues etc. I noticed it was usually small things in the back of a car (away from the driver) that people didn't catch. Like broken buttons or led lights in the second and third row audio/AC controls, speaker rattles on rear speakers, dead rear surround speakers, missing plastic covers on rear seatbelt anchor points or seat bolts, missing fins on rear AC vents, missing floor mats, missing jacks and/or factory tools..etc.
3. Preventative maintenance is great and a rental car company isn't going to sell you a broken car. They WILL however sell you a prematurely worn or misused car. This isn't malicious and it's almost impossible to detect, but it's the nature of the rental car industry. Here's a few examples..
--I've seen customers use 4WD inappropriately on rental trucks (i.e. using 4HI on dry paved roads). While this won't cause any immediate problems, it can lead to a shortened lifespan of the transfer case over time.
--Customers and employees routinely do things like leave windows and doors open in the rain (for longer than a typical owner would) or leave the car running for long times. Again, these things won't show any immediate damage, but could ultimately lead to issues own the road.
--Most customers put in the cheapest gas around in a rental. (Which means alot of no-name fuel)
--Customers will also tow or pack a rental beyond the recommended limits. (Most of the time, they don't even know these limits are a thing)
Can all these things happen with any leased or pre-owned car? Of course. But statistically, the odds are higher when it comes to rental cars. And because rental cars go through so many drivers, usually a rental is exposed to a wide array of not-so-nice behavior...vs. one or two previous owners with specific bad habits.
Just my two cents and food for thought.
