They won't be in cities, or at least most won't. If there is a decent housing market, when something pops up from an estate in that range, somebody will grab it quickly and work to flip it.
I've been shopping, I use Zillow. I set up what I'm looking for, they send alerts to my phone. Really low priced properties are either stagnated by legal problems or turn over very quickly, so you need to be able to act quickly. There are other real estate search engines, I've gotten used to this one.
Low priced housing is usually rural or in small towns that are almost ghost towns, available all around the country, not just Florida. I'm finding properties in the Missippi Delta, rural midwest, the parts of eastern Texas that used to be cotton belt. I can find lots of cheap properties in Oklahoma, Kansas, eastern New Mexico ghost towns and nearby rural areas. Florida is a little more difficult and must move fast, you are competing with investment buyers.
A typical $20K to $50K 2-3 bedroom home built in the 1930s to 1950s will need that amount of money again to be marketable to someone who actually wants to live in it. I've got one right now the appraiser says is $83K for the purposes of taxing me that needs $20K worth of work before I can rent it out or sell it for $50K. I don't want to talk about what I already have in it, it was a bad choice.
Florida is really tricky. Visited family there for 50 years, lived there two years, mostly when it was one of the cheapest places in the country to live, ambivalent about living there again, things can change really fast. Rural property can be overwhelmed by development, once "hot" properties can collapse on natural disasters. People are becoming more aware of the flooding problems, sinkhole problems, things to which we once turned a blind eye.
If I were looking for cheap property safe to live on the next 20-30 years, maybe Hernando County or Pasco County away from the coast, and some distance from the major highways, or Levy County well outside Ocala. Old farmsteads, mostly.
A nice modern place in a developed area? Not at the prices you are talking about.