Florida should be busy currently with people staying in the Winter to get away from the cold & snow. 

It is the Winter time so it's a slower time but I think you are overpriced.

I would keep them at least until the summer because it is not great to lease in the winter. 

You might consider buying this winter since houses are on the market 60-90 days right now and you have a good negotiating position.One positive on the higher interest rate is that you can deduct the interest and lower your taxes.

Construction didn't start until Fall/winter 2019.

In addition, I am considering changing my furnaces/boilers to have plug-in cords instead of being hard wired so that if there is a power outage in winter that I could power that heating system with a portable power station.

I would like to buy a future retirement home to get away from the cold winters but in the meantime would love to rent it out as a vacation rental.What are the good areas to consider and where would I get the most vacation renters and cash flow?

Think of all the horror stories about tenants maxing out the heat with their windows open during the winter, deliberately running water bills up, etc. 

In fact, I just tossed away an amortization book of tables that I've had for almost 30 years, when we were doing some winter cleaning - the lowest rate it went down to was 7%.

Winter time is rough for renting especially in states like IL with rougher winters.