Would it be possible to just install an egress in the basement bedroom, and leave the living room unchanged?

Hopefully they all stay but if one leaves I will update the unit and be able to rent it for about $250 more per month. 

As far a the instance is concerned many of the insurance carriers offer a discount when combining home and auto insurance.

My main concern is rent.

Maybe I'll try that - my only concern then is I don't get the chance to learn by rehabbing the home with the contractor and asking them questions (unless I wanted to make multiple weekend trips down).

If you guys can bring your principle balance down to ~ $250-300k, you could refinance before you leave and bring your mortgage payments around or below $1800.

They have informed me that they are not leaving their home.

Rents are strong and vacancy low.The obvious concern for these markets is that the lack of population growth may worsen and actually begin shrinking.  

I share your longer-term concern about anything even near a beach as ocean levels are rising and there is evidence that hurricanes are strengthening.  

Call everyone back whether they leave a message or not