Almost everything I ever built that was two story (1980-2000) used a 3/4 inch sheet product called redex. This is a water resistant particle board type stuff much stiffer than 3/4 plywood. Truly very water resistant, this stuff, but still a wood product. In one case, 3/4 plywood was then overlaid with ordinary 1/2 inch particle board. That one was not water resistant, and the floor had gotten damaged before we got a roof on the apartments.
My mobile home, it was nothing but cheap 1/2 inch particle board, and after 15 years in it, we were quite familiar with the sink straddle. you know, can't stand directly in front of the kitchen sink anymore, or you'd risk going through the floor. That trailer btw, had the plastic pipe and fittings that lasted at most 10 years, so it's plumbing leaked like mad everywhere.
Only one way to find out what your condo has, Peel back a corner of carpet and see. The waterproof flooring will look like particle board, but a dark color and almost waxy feel.
This is all for inexpensive wood frame structures with wooden truss floors. If your condo is made more like a skyscraper, then it will have steel trusses, and each floor will be poured concrete a few inches thick.
Before you buy a house or condo, find out what it's made of, what is the floor, etc. Don't just ask the realtor dumbass, they don't know shit, and will say anything and honestly think it's the truth. If they won't let you poke and prod, hire a house inspector before you close, and let him tell you what you have.