I'd first find out who filled it and how it was filled, pool debris, concrete isn't a problem, but if the pool filter and pump equipment was tossed in the hole there could be a void.

The air conditioner manufacturers are going the way of the automotive company's so you have to use their parts on newer equipment coming out.

You can do investing many ways.I personally like apartments and NNN properties and it's what I specialize in.One that I didn't see mentioned is investing in businesses and or flipping businesses.You can find an owner wanting to retire and you put 25% to 50% down and then finance the rest.You can also find someone who wanted to own a restaurant for example and buys a business a runs it in the ground.I see this often with people that have retirement savings and want to put the funds to work and do something.They think having a business all these people will come in or keep coming in based on what the previous owner is doing and it will be fund to run it.After running it in the ground they are ready to dump it cheap.You let them pay for the expensive buildout and all new equipment and then pick it up for next to nothing.You put systems into place and turn around and hold long term for cash flow or sell it off for a profit and do it again.These are my main 3 categories I focus on for myself and my clients.I also like raw or semi-developed commercial land that can be sold off for a big profit.

I explained I owned the house, was living in it, and all the lifts and other equipment was rented.

While I'm on the topic, do you guys add provisions for things like playground equipment like swings or on-ground tree-houses?

Sounds like you will be better equipped for the next one

There are social service agencies that are far more equipped than we to handle the situations of homeless families. 

I'm really at the basics level with questions like:  What costs for tools, equipment, supplies should be treated as business expenses and what should be included in adjusted basis? 

Buying commercial property can be depreciated using MACRS instead of straight line, meaning you can depreciate a large chunk of the property right away.Think things like solar energy equipment can be depreciated by MACRS as well.Not an expert on this though, would recommend verifying everything with a CPA.

She then went on to explain what systems need to have a value assigned to them: -HVAC systems ( motors, compressors, boilers, furnace, chillers, pipes, ducts, radiators) -Plumbing systems (including pipes, drains, valves, sinks, bathtubs, toilets, water and sanitary sewer collection equipment, and site utility equipment used to distribute water and waste to and from the property line and between buildings and other permanent structures)-Electrical systems (including wiring, outlets, junction boxes, lighting fixtures and associated connectors, and site utility equipment used to distribute electricity from the property line to and between buildings and other permanent structures)-Gas distribution systems (including associated pipes and equipment used to distribute gas to and from the property line and between buildings or permanent structures)...