So it really depends on the particular circumstances.

I know when I injured my knee at home, my health insurance provider had me fill out paperwork detailing the circumstances of the injury and certify it was not employment related.Regardless of the employment situation, someone was injured on your property, so you may be liable to them.

Depending on your circumstance and your comfort level 100k is great place to start for multi family investing if you are open minded to house hacking. 

There's circumstances where this totally works but given the low rate climate today and if you're planning on holding onto the property for the long term, better to lock in the rate and secure yourself for 30 years rather than gamble in the market for 5-7 years ahead. 

I've got about 2-3 paintings of nude women on every wall in every STR house. 

Whether you are engaged in a trade or business is a facts and circumstances test.

You won't be able to deduct it this year under the circumstances you presented.

If your circumstances change after the fact (such as a job relocation like you mentioned) then you may be able to get out of that requirement; however, if your intention from the beginning is to move out in less than a year then you’re walking a fine line with committing mortgage fraud.

The situation is similarly complicated if I pay for the duct cleaning and the tenants agree to reimburse me.I have come to believe, anyway, that duct cleaning is at best of no value and at worst a scam, except in certain unusual and specific circumstances, none of which exists here, and it can be damaging to the house.

I know in a normal circumstance, if the dishwasher stopped working I would obviously pay the bill.