I would definitly persue the offer to learn more.
I would treat this as an equivalent of a reverse mortgage. As far as pitfalls, try to find a sample reverse mortgage contract so you can see what protections are in place. You are most interested in protections of the lender, not the borrower.
For example, who provides the maintenance, and at what time frame? Can they do what they want with the property, or do modifications need to be approved by the new owner? If the place is trashed, can his/her estate be sued to recover damages?
You would also need to calculate "lost rent", and appreciation for the duration of his/her life to see if you would come out ahead.
I would only be comfortable with a sale that occurs occurs on the front end, with a 99 year non-transferable lease for $1 per year, with all other costs included in the contract. If they are still the registered owner at death, I would not have any confidence the deal would be completed after death.
Keep us posted.