I have lived in central FL for over 24 years (Winter Springs in Seminole County). Since you are building in the Villages, just south of Ocala, you will need an independent cooling/heating system in the garage, freezing temps in Ocala are not uncommon. Assuming you are building a concrete block home, your best bet will be to insulate the interior garage walls with foam sheets and paperless sheetrock over that. If you’re thinking of building a stick home I strongly recommend you reconsider (hurricane and/or tornado survival). The biggest issue will be finding a high quality fully insulated garage door, the garage door will be where the most heat and cold intrusion will occur. If your water heater will be located in the garage you may want to consider a heat pump water heater, you will basically cool the garage for free while generating hot water, I have one in my garage where I store a portion of my collection.
I noticed a few members recommending copper water lines, be careful with copper, since your home will be built on a slab any water lines imbedded in the concrete must have a sock lining on them, including copper, to prevent corrosion. In addition, the copper below and thru the slab MUST be SOFT copper! I hear nightmares every day about water leaks in copper lines not properly installed and/or the use of rigid copper. If your contractor balks, find a new contractor.
