If the person stops making payments, they alas,  have to foreclose.

None of this has anything to do with your personal tax return.

So I wonder if I can sell my home in Idaho, purchase the new one under my personal name, then how many months or years must pass before I can setup an LLC as the owner of my primary residence, or if you think that will be a good idea? 

Imagine making millions of dollars over the course of your career and then having to pay 30-50% every year to uncle sam instead of compounding that cash over time.This is exactly what real estate professionals have learned to mitigate.To reduce their taxable income, they just buy a building every year, do a cost seg, and use depreciation to reduce their tax liability dramatically.Their personal wealth snowball grows much larger and much faster than their W2 counterparts who give most of their money back to the government each year.Following this strategy as a real estate professional is one of best ways to end up with a much larger net worth at the end of your career.

The person I would seek advice from is a CPA about this. 

Personally, if I were to sell the stock, I would buy more property, not pay off the existing one. 

Is 10-15 miles too big of an area when determining the unit count per person?

I think it's just for text, not to talk with a live person.

I personally have success in doing flips with my partner here in Ohio.Lakewood and Edgewater are gentrifying neighborhoods in Cleveland.

My personal preference for a buy and hold would be an already established area (or an area that's still gentrifying, but has already seen significant progress).