I'm sure you'll find that this is a fantastic community of people who are glad to help out.

In some jurisdictions you can drain the gray-water into a flower bed.

When I went to enter the apartment to ensure the outlets were working again I was greeted by her dog (deposit paid) and a second large dog of which I wasn't aware.

@Tosin Oluwatoye a good way to test out your location is to put the concrete pads down, add a 30/50 amp outlet and water line, and then rent out the pads to people who already own their own tiny houses.

That you wisely build in the costs for replacement linens and towels (also offer black face towels), possibly don't use high-end top-down shades in the Bunk Room (although those black out shades match all the shades in the rest of the house and it's a high-end property), chalk can be brushed, semi-gloss on walls for easier clean-up... and yes, there are clear check-out directions to run the dishwasher provided via an online guest book, a physical guest book, and an email I send regarding check-out the day before they check-out.

Outlets/switches may need to be moved or can possibly be eliminated. 

Feel free to reach out.

Being a very handy person and an engineer, I feel confident that I will catch all issues.For example, I just noticed that I have a couple of loose electrical outlets.

Somebody that really wants to get in can still do it, but it might help provide peace of mind for tenants.Those size A/Cs will run on a regular 120 V circuit, but you might look around to make sure there are outlets close enough to all the windows you want to put them in. 

It is no different than maintaining the electrical outlet for the W/D or the plumbing for the washer.