During my inspection period, we noticed signs of an oil spill around the tank outside.

When you are this far, and you orient the toilet straight and tighten down the bolts, but not too loose so the toilet won't rock and not too tight so you don't break the porcelain & with the tank far away enough from the wall so you can fit the lid onto the tank but not too far away so it doesn't rock when people sit on the thing and when you connect the tank to the bowl you remember to use the rubber ring and when you insert the ballcock stem you get a good seal and you set the water to stop before it overflows the tank when you turn the water on and you use plumbers tape on the threads when you connect the hoses, you should be fine.

Most do, but those who don't let the tank run dry will gunk up the service resulting in expensive service calls.

Just know that a 2nd system (new power meter, separate oil tank, 2nd gas line/tank) will require a larger upfront cost and your city and utility companies will likely want to come in, and double check everything you've done (more time and money).

The only thing I would add is to use this in conjunction with CoC (or another useful metric).For instance, if you can make $100 a door with no money down that's beautiful but if it takes 20,000 to get there then that will TANK your CoC.

HVAC includes new furnace, refurbished air handler, new water heater and expansion tank, sump pump, and some duct work.  

We have a septic tank and City water.

Doing this will also allow you to install water sensors in the basement to detect flooding or leaky hot water tank.

I have a 36' travel trailer (like a 2 BR house on wheels) and we carry our own water, holding tanks & have our own power, so we don't need any hook ups.

Trouble free tenants (knock on wood), and I think the only thing we've done is pumped the septic tank over the last 4 years.