Now I spend my time making sure new investors entering the market do not make the same mistakes my wife and I made. 

Regarding vacancy periods, you'll need to understand, Days On Market (DOM) - or find a great PMC that understands and can explain it to you.

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.: Wild idea based on a property in my local market.

Especially in a market where 95% of the buyers, and 99% of the highest offers come from owner occupants.

I would compare the return on your rental to your stock market portfolio.

As far as which market, I'll leave that to realtors and investors in Florida.

Any idea how the inflation & high interest rates affected the RE market/s? 

The Long Island market depends on your goals.

An ADU could rent for an additional $1,200–$2,000/month, depending on the local market, potentially doubling the property's cash flow.