Stay away from rentals, especially trucks (though that's an "SUT" according to GM) and 77k on a 2015 rental? I mean, my mom has 80k on her 2014 Wrangler but she does a lot of trips and drives 60 miles a day for her job...
I actually do like that body style Suburban/Tahoe/Avalanche but... the thing with rentals is: "Well maintained". Yes, it may have had service checks every time it was used and regular oil changes and inspections, but the mechanics that do it work for a corporate company that only cares about making money off of people i.e. "Just fix it as fast as you can" So shit will start to break within a year.