Well I can tell you what I see
Overall tractor appears to better than average for rust, has new paint on it, looks like it's all there,
BUT the charger is in pieces and most of the control circuits are missing, wiring also ???. It would be a big job to put it back to original working condition and cost some $$$.
IMO this is a good candidate for an Alltrax conversion, if your going though all the trouble to rewire it might as well use modern controller. In the end it will be a better working tractor.
Plus it needs a new battery pack, either 3 big 12volt batteries or 6 golf cart batteries (6volt).
It has with a late model mower deck that looks good but can't tell if the rear roller is there in the picture.
As to whether it's worth $500. as is, ??? be nice to get it for less.
Controller = $500.
Pot box for controller = $100. +
Batteries = $300. +++ minimum
Plus charger and whatever else needed to finish. $$$ ???
It can get expensive.