But once again... it could collapse tomorrow, or go on for another decade.

You should be able to float a 400 note for 24 months after your roof spontaneously collapses on January 31st, 2032.

My vote is to repair, repair, repair.Water damage can lead to significant problems, from blistering / peeling paint to ceilings collapsing and electrical shorts.

If the deal collapses and I would lose everything, I'm out.

Newer building has seen huge increases in insurance in the past years because of the collapse of the Champlain Towers and hurricanes, but that is over and there is more competition now in the market: I have already seen the cost of insurance going down -8% in the negotiation for 2025 in one building where I sit in the HOA. 

Just a few years later, property owners were under water after the economy collapsed.

Usually, only heating oil USTs associated with commercial properties are regulated. thus, most home heating oil tanks may and often are taken out of service without any oversight from state regulators.Second- the rules that are in effect for heating oil tanks are usually less stringent than for diesel or gasoline tanks since heating oil tends to thicker and may not migrate as far. as a result, many states just require tanks to be cleaned out. they may also require the tanks to be filled with sand or concrete to prevent collapse. but sampling may not be required.Third- the key to determining if a tank has leaked is to collect soil samples from around and beneath the tank (groundwater also if groundwater is shallow). another quick way to see if a tank is leaking is to "dip" it with a stick that has a paste that turns color in the presence of water. generally, if water has gotten into a tank, it can mean oil has leaked out of the tank (although a certain amount of condensation may be present even where there is no leak so this is not a infallible test).Fourth- if there is currently a tank in the basement, ask the owner if there used to be a buried tank (a/k/a underground storage tank).Fifth, If the tank has impacted the soil, the cleanup generally varies from $25K to $50K though the costs will depend ont he depth of the contamination. i once had a home with a heated pool that had pressurized piping and used diesel. the contamination went down 40 feet and the consultant went crazy excavating the soil to the tune of $400K!!!

If the deal collapses and I would lose everything, I'm out.

I am looking at starting a wholly owned LLC owned by my sub S corporation, then hope to transfer real estate into it and take notes back, then collapse the Sub S leaving the LLC owning everything. 

Steal Industry, auto manufacturing, the facilitating things to these like coal mining, the decapitation of these industries in the US has left a trail of devastated towns and collapsed markets who have NOT come back and have no prospects of ever coming back to there former glory as the "thing" that put them there, is gone.