Only buy property of a long established star, one who is already established as one of the all-time greats. Jimi Hendrix would do, with the added benefit that he isn't around to have any more guitars. The established best,in whatever field of collecting, is always going to hold its value better than anything else.
And above all, get well proven provenance, proof of origin. This is usually of a trail of ownership back to the star, supported by pictures of the instrument in use, diary entries, invoices, recollections in autobiographies and the like.