Earlier this year we replaced the original water heater (I am sure the new one wont last 33 years).They will be gone as of September 30th, then begins the rehab and renting process. 

However, this new buyer is threatening to get attorneys involved because he seems to think that this is not a encroachment granted in perpetuity.I think my folks are in the clear on this due to the nature of the language in the agreement but the last thing I want to have happen is get lawyers involved and have them have to pay to move the tank since, technically speaking, they are in the wrong.Don't have any experience/advice in this matter?

However, last year my mother began showing signs of early onset dementia.

Its back on the market as the last buyer didn't have enough cash for the liens.  

@Michael Swan Last I heard was around mid 80's.

Last time I had to withhold from the deposit I had a mini-dissertation with images.

NE Ohio has had a tornado and a couple of fires over the last 50 years, so not sure there is much of a risk.

Borrower paid single premium is when the insurance company charges a lump sum at closing, rater than monthly fees that last until you hit 20% equity by amortization.

I actually bought a 4 unit a mile away for $45,000 last year but that needed about 30K worth of work so I feel this is about right as this one is turn key with no repairs needed.The seller financing deal - Sales price $63,500Cash at close from me $50004 year note @ 4% for remainder ($58,500), monthly payment of $1000 with balloon at the end, no prepayment penalties.Monthly projectionsIncome =     $2200Expense=    $220 management                     $220 CAPEX = No problems yet but "Unknown age" on the roof and owner has had property for 20 years                     $480 Insurance/taxes = Total taxes for 2017 were $4982 on assessed value of $78000 plus $600 a year for insurance

According to the tax record the last sale was in April 2017 and his post is from August 2017.