If you are only living there for a few months each year, why not look for a home with a suite? 

He'll have at least $2k per month in positive cash flow and tons of equity when it's time to find the next home in some years.

Building departments, typically, are very helpful. 

If your home is newer, requires little maintenance, and doesn't experience a vacancy for at least 12 months, your $300 cash flow can build up a tidy reserve to get you through.

They may have even inspected your primary home without you knowing. 1) I have no idea.

At appraisal it was worth $500K and it is in a neighborhood where homes that are on a third the size of the lot are going for $800K.What's the best way to get a loan, about $150K, to rehab his house and get it ready to sell.

Sometimes people list on Airbnb but I think you're getting people who are expecting a typical vacation rental.

I have an HELOC on my home.

It is a bad idea to screen and then show homes with a smart lock code that I can change? 

If your first investment goes South you run the risk of putting your home in jeopardy.