That is an impressive rate!

House hacking is a financial no-brainer, it eliminates you single biggest monthly expense, so you can increase your savings rate.

I also am very interested in purchasing more STRs, and this is a really low risk way to see if I'm up for it (we have a 2.9% interest rate on our mortgage).My biggest concern is an ongoing plumbing issue we have had.

The rating systems for short-term rentals has lost all validity.

The default rate is only 1% per month which is 12% annual.I assume there are more pages to that agreement

That is the best option if you are truly trying to help a family member.you cannot get control of the mortgage, you can do sub2 but you are not in control, the bank could call it due if they see the property transfers title.The other way is for you to buy it from them at market rate, then rent it back to them at market rate.

One your loans will be a higher interest rate, next you will have annual filings, the cost of a registered agent every year, and items like that. 

For crowdsource investments on Republic, StartEngine, etc there's a great resource called Kingscrowd that reviews each investment offering and gives details and ratings on the team behind the project.

How about the interest rate - is there also a different rate for citizens and non-citizens?  

@Jonathan Small government actions have led to an unprecedented 40% increase in the money supply, 50-year record inflation, record increase in interest rates, bank failures, credit tightening, CRE recession, housing affordability issues, mobility issues, inventory issues, and massive impacts to the world economies, every investment class, and our families, kids, and friends like never before.