The previous owners invested over $12M into building it between 2009-2012 but then left it vacant for years, allowing it to naturally age.

In general, a turnkey can be a great way to avoid conflicts with those rules because of the highly passive nature of the investment. 

✅ Low operating costs✅ Low crime rate✅ Low risk of a natural disaster✅ Sufficient population to have economic stability, major highways, and a major airport.

Can you please elaborate why the business activity nature of STR will be treated differently due to part of the property being primary residence and under which rules?

Based on what I remember, it gets even more complicated if the 401k is from a previous employer.In your case, since Fidelity is declining the account due to the nature of the retirement funds, one option might be to consider rolling over a portion of your 401k into a self-directed IRA, which typically offers more flexibility.

It's human nature. 

From there you will likely naturally grow by referral, and host will give you experience in how they manage what it is they need you to do (something you would do yourself when you're a host/co-host).

Naturally, that has led me into looking at some different markets.

Also ask who the natural buyer is if you choose to sell the property they sell to you.

The best benefit of syndications is the passive nature and the amount of information you can gather.