I knew a gentleman who made a business out of finding hangar-queens, cleaning them up and flipping them. This works if you can get clean title at a steep discount and if you are partnered with a IA who can make the plane flyable and sellable. My favorite plane in his inventory was late Pa28-235 that spent 18years parked.
Most planes that were in good shape 10 years ago when they were parked will start right up with a new battery and fresh fuel. After you relocate the plane to your hangar you do things like replacing rubber pieces, install an ADSB transponder, buff up the paint. Your IA would have to check for any show-stopper items like a crank that is under recall etc.before you make any commitment.
With the estate issue, you just need to be certain that the person selling is authorized to do so. If he isn't, this can bite you when either:
- the FAA rejects the registration and you don't find out until after you installed avionics etc.
- other beneficiaries of the estate note that the 'expensive plane' is gone and now come after the seller for their share of the treasure. While their claim would be against the party that sold the plane without authority, you could be part of the festivities if it goes to court.