As for supposed warranties, they are a sales tool, not a service tool so, buy the car on its merits, not based upon its warranty.
I wouldn't necessarily avoid a rental. Most are auto so, there aren't the manual trans
issues, the cars are shockingly expensive to rent when loaded up so, it keeps the riff-raff out of them and they tend to have extremely low mileage. If the car passes operational inspection, there is no reason to say "no way" to a former rental.
2014 Premium GT, SGM, Brembo, Auto, Tech, Comfort, etc. GT500s, Steeda UCA, VMP auto tune, 100 shot on BBR tune, best et: 11.38 at 120.85
2012 GT, Candy Red, Brembo, 3.73, Tech, Comfort, etc. Procal tune, Roush upper, UMI LCAs, Steeda red bracket, GT500s, 28X10X16 Hoosier slicks, best et: 11.91 at 115.23 RIP