There probably aren't that many investor buyers in Spearville and the installment sale would spread the income tax burden for the seller.

It appears to be on a reservation because the Bureau of Indian Affairs is involved, @John D. and it also appears that that it may be a contract for deed (land contract, installment sale contract) where the seller received full payment over time, but never transferred the ownership to the buyer even though it was fully paid by the end of the contract. 

I don't see why you're prevented from installing a lawn this year?

I would check with a local HVAC (Hydronic) wholesaler or installer to see if you can still obtain them {be prepared for them to cost almost the same {probably more when you factor in labour} as replacing the entire unit.As for using PEX, I'm not certain if the heat-rated PEX (used for in-floor hydronic heating which runs around 140F) can be used for a boiler and radiators (which typically run around 180F).  

I had to do a decent amount of work yes - I needed to overhaul the plumbing, stain the kitchen cabinets, replace vanities, install appliances, and redo a couple of doors and light fixtures.

In NVsell on lease w option, no title exchange, landlord tenant relationshipsell on seller financing1. free and clear house, note plus mortgage or note plus DOT, title transfers, if default need to foreclose2. existing first mortgage, sell on a wrap or installment sales contract, due on sale issue, title transfers, if default need to forecloseHope that helps

Cabinet installs.

I can tell when people arrive because they adjust the thermostats once they arrive.I will be installing a outdoor security camera in the near future.

Vinyl floors can cost as little as $2 a square foot and they're easy to install.

While most Net Zero buildings are energy efficient, perhaps even highly so in comparison to minimum building code requirements, there is nothing requiring them to anywhere new the efficiency level of a Passivhaus   .... this is why you will see odd things like warehouses with large rooftop solar installations being able to claim Net Zero.On the other hand, Passivhaus sets three metrics which a building must meet to be certified as Passivhaus compliant:  The building must have a heating and cooling demand of not more than 15 kWh/m2 (4,755 BTU/sq ft; 5.017 MJ/sq ft) per year  and a peak heat load of 10 W/m2.Total primary energy consumption (energy for heating, hot water and electricity) must not be more than 120 kWh/m2 (38,040 BTU/sq ft; 40.13 MJ/sq ft) per yearThe building must not leak more air than 0.6 times the house volume per hour (n50 ≤ 0.6 / hour) at 50 Pa (0.0073 psi) as tested by a blower door.Ironically, the research and pilot projects which fuelled what eventually became the Passivhaus standard was carried out in Saskatchewan as a National Research Council (NRC) project in the 1970s (the house is still in use today) and a similar project (Minnesota?)