If STR regulations come to the area, my plan is to do MTR and while it is not as much revenue as STR, I should be able to generate a decent return over a 5 year minimum hold. 

1) The regulation 1.263(a)-(f) reads that you're able to utilize it for amounts paid during the taxable year.

At one time this was allowed but is no longer legal or acceptable under RESPA regulations. 

I converted my garage to an ADU and now my main house is considered RSO unit since it was built before 1978. I have been airbnb’ing it less than 120 days which was helping me to work/ travel a portion of the year outs...

Diversification across 3 markets also de-risks my investment if local regulations or micro-factors shift negatively in one market.

There is federal regulation against it buddy. 

How do you ensure that properties comply with local regulations and ordinances?

Hey guys What do you think in general for STR in both of this cities I came back from Miami and what ever going on there it’s crazy , I also like Austin area alot but I know more regulation for STR there , in general I think the rental market in Austin it’s not good Median rent is 2-3.3K and house pricing is 400-700K  so it doesn’t worth for long term investment and cashflow , maybe only for appreciation.

The above are made up numbers that will vary based on your market and local regulations but you get the idea. 

Investors can purchase a portion of several properties in the form of shares.Real estate investment funds provide you the chance to invest in real properties with a variety of rules and regulations that are specific to each region.