Well obviously a John Deere branded mower, Looks to either have Overhead valves or a Overhead cam, by the valve cover.
Looks like a briggs engine, they're generally easy to work on, probably just a gummed up carb from sitting. If you do look at it, pull it over to be sure you dont hear any knocking, just in case the connecting rod is toast.
if it were me i'd probably offer in the neighborhood of $50....
EDIT: looks to be a John Deere JS63VC Variable Speed Mulching Mower
https://www.mowwithus.com/garden-machinery/mowers-petrol/john-deere-js63vc.html