that's a wise move.. and the weather is better than areas that are prone to thunderstorms and high humidity ( Houston) and severe cold.plus is a fun place to visit and no income tax if you can take residency..

It is extremely moist down there and we have had a stretch of 90 plus degree weather with extreme humidity the last 2 weeks so we are now worried about mold.

I've spent a lot of time in beach houses and houses in generally humid climates, and they never have a mold problem any more than any other house unless there is a leak somewhere and/or no air circulation.The other thing is that lots of people jump right to mold when something is really just mildew like can happen in a bathroom that isn't cleaned often.

If it's still damp now, rent a couple of commercial fans and dehumidifiers to reduce the humidity. 

Cracks depend on a hundred different factors such as humidity on the day of the pour, ambient temperature currently, ambient temperature on pour day, etc. 

It’s always hot humid and muggy this time of year.

The materials used in making these drive the quality and the cost;  - Particle board (and there are different grades of this) is the cheapest  - Plywood is better (again different grades)  - Solid Wood is best (and again different types)Water is the enemy of wood in general and cabinets specifically due to humidity and leaks so I prefer solid wood frame with plywood decks / shelves.

Add mold and mildew spores and high humidity and you have a recipe for more problems.

Have you gone through any warm humid weather yet?

Temperature is cooler in the summer than sw FL.Fort Myers / Naples is less expensive, more retirees, small town vibe, hot and humid in the summer.Both areas are great for vacation rentals.