Might be cheaper to just repair the motor if anything is wrong with it. Might need some adjustments and cleaning out but who knows! More information is really needed to know what the issues will be. Example, if water has gotten into the electrical system all the safety switches might need to be rewired which can be a pain.
If I were going to take on a project I would get it running, paint it up nice, and sell to a homeowner or startup guy to turn a profit. Especially if you paint it up and it looks nice, people will pay good money for equipment. Obviously I wouldnt let myself sell a lemon or a mower that will die in a few hours use. Or keep it as a backup, but I dont have a need for one so it would just sit longer!