If you're just going to hold a couple of properties, the cost benefit analysis may not pan out, and you will definitely get sued personally if your LLC gets sued.

Flushes the toilet?

Now she complained the issue of toilet fill valve which caused unreasonable high water bill and claimed it belongs to wear and tear and a plumbing issue.

It doesn't sound like he's tried to take advantage of you, it's just that the deal panned out in an unexpected way. 

., microwave, diswasher washer dryer$10000 plus the GFI and power outlets $3007) input new light fixtures$3000 painting of the whole house$4100Clean up $ 400temporary toilet $500temp power?

Typically Investors complete a 1031 exchange out of active ownership/management into a DST because they are looking to defer capital gains and stay in real estate to build their wealth but are tired dealing with tenants, trash and toilets. 

Not sure how these STR numbers pan out, but the opportunity is limited and they sell in hours.

luxury portable toilet rental I heard has good cash flow for business.

I can't imagine maintenance on brand new tiny homes would cost much, especially if you did composting toilets and rerouted any grey water to a garden or something you'd have no plumbing to worry about. 

If the tenant calls you at 11 pm on a Sunday about a toilet overflowing, how will you handle it?