To save others the trouble and for curiosity sake, I contacted FamilySAFE Certified Tornado Shelters and Safe Rooms to find out the cost of a in house shelter that could be placed in the garage. The cost is not on their web site. So, I will let you know.
The Family SAFE | Certified in-home Tornado Shelters and Safe Rooms
The Florida dealer's web site, which may not be current lists pricing starting around $4,000.
FamilySAFE Shelters | Storm Shelters, Flood Evacuation Vaults & Gun Vaults
My wife, who is a little claustrophobic, might not like this approach.