You have 2 things in your favor with this saw
First off, it probably hasn't seen many hours of use because of its size. Second, the rental place isn't going to let any moron use that saw. The local place here was skittish about renting out an 036 until I gave him my background. Didn't rent, was hoping they had a bigger one I could have.
And, yes, they usually maintain their stuff really well. Rental places don't get paid if the equipment goes down on the job.
If the price was "right", I'd be in. As far as price, look for a history on ebay. It will at least get you in the ballpark. Condition of the chain and bar should be taken into consideration, but, I think If you could get it for $400-500, you would be doing good. I paid $425 for an O66 (comparable Stihl) that was a good runner, but was well used, with a serviceable 36" bar and no chain. I feel good about the deal, even though the clutch will eventually have to be replaced ($80), it is worn, but will still stall the saw like a new one would. Until it slips, it stays.
Good luck, and have fun.