the question begs to be asked...
why on earth did you register this in the first place? if you saw value in it, maybe this person sees the same thing
the appraisal request is a red flag, but on the other hand any chance to sell this one for actual money should be welcomed as a once-in-a-lifetime opportunity and pursued with vigor. by all means, do not invest any money in an appraisal. if nothing else, tell the prospective buyer that he can do it and you'll deduct the cost of it.
let us know how it turns out