Better to not get refrigerators equipped with water and ice dispensers ...

I live in a rural area in Texas and am considering acquiring a neighbor's three acre place (house, land, equipment). 

I could fill the hole with equipment and properly tamp it, but what would need to be done to go about it properly?

Your biggest con is that you are operating what can be dangerous equipment in a public area without supervision.

It may be LL responsibility but it's more likely that it is on the tenant, which they are responsible for the service/maintenance of the equipment. 

But, she has a $500 annual deductible on repairs and replacement of equipment, so basically she already agreed to that, and as I told her, for that one time up front payment of $500, you're basically betting that you'll be staying here at least 4 years to do slightly better than breaking even on your deductible.Yes, I know R-22 is on the way out and getting harder to find, but it's not reasonable for me to spend $8000 on a new system just so the tenant doesn't have to pay $150 - $200 per year to top up the existing system.

We also added AFCI protection at the breaker for the bedrooms, per current code requirements. 4) All of the new receptacles that are on the existing ungrounded 2-wire copper circuits have been labeled with "GFCI Protected" and "No Equipment Ground". 5) New circuits have new wiring. 

When a tenant moves out, the companies tend to leave their exterior equipment behind, junking up our property.

After the initial airing out, good ventilation should continue until the cleanup is finished.Spilled chemicals and supplies may have contaminated non-lab equipment.

Maybe a $10.000 equipment lease or something like that but nobody will give you unsecured funding right now.