I went to the website internest.com
You can find builders which would build a £70000 house on a $10000 lot of land which you can find plenty.
Or in Okeechobee for $88K for 3 bedroom house.
There are plenty of houses around $100K. They do not include the incentives you can negociate with the builder.
Now, would one want to buy in Florida with the hurricane threat, high taxes and insurance? I am not sure.