In New Hampshire, title laws are strict, so we couldn’t move forward without obtaining a signature from a living heir.The title company dug deep and eventually located a distant relative—a niece of the deceased owner, two generations removed.

I am sure there aren't many comps that this would generate.

They just generate chlorine at a constant rate depending on the system setting.  

. - if I use my cash, the investment needs to generate > 5%.

(This well could be a generational thing and whatever the comfort level of the guest is.)

But if you were to use it as an air bnb or ir it is raw land that you can generate income from by farming or renting out to farmers or grazing that would certainly work.

Deflates property values.....interesting future.

Because you are essentially buying into an existing business, the sale of it could generate a disproportionate amount of tax for you given your time in this deal.

Having a co-signer doesn't feel like that at first, but you can't predict the future.

Selling at FMV avoids the gift tax but provides your child with a higher tax basis, reducing their future capital gains liability.A better strategy for selling below FMV is to sell the house at FMV on an installment note, then forgive interest and principal annually up to the gift tax exclusion amount.