If you have proper systems and practices in place and do a reasonable job at tenant screening, the risks can easily be mitigated and there are actually several benefits.

I like Airdna, its not perfect but I like to use their broad market report, then look at specific zip code reports.

The agent told me it is a pain to move a post office and no benefit for them to sign up for the extra work involved. 

I'm not going to give him that much benefit of the doubt. 

It depends entirely on your specific state codes.

Try using city-data.com and Trulia.com for information by zip code.

There is a reasonable chance that you could be required to convert it back to a 2 bedroom, so you would have paid for the extra square footage I would expect to pay for the original square footage and have the price discounted from that for the extra hassle and risk of dealing with the code enforcement officer 

If you still have US real estate assets when you pass away your heirs will still benefit from the stepped up basis regardless of their residence so that shouldn't really factor into the equation.  

Husband has good job with good benefits but gets laid off.

The biggest benefit of this arrangement was actually keeping track of the hours.