Wow. So many unknowns. First of all, everything changes, nothing stays the same.
Second of all, I agree with Carol. Consider being a snowbird. And the NYC area is much cheaper airfare than here in South Florida.
Another consideration is medical care. If you do "live" in SXM for 15 weeks at a time, that can be an issue.
We bought a place there rented it out. Worked out well financially.
Think more! Nice dream though.
Good luck.
irina