From your description, it sounds like the actual floor, and not the whole unit bouncing when you walk. If you only have support of the wheels and tongue (even the stabilizers don't help much) your squeak could be the wheel suspension
But again, like everyone else mentioned, without much detail, its only guessing in the dark.
Mark, Vicki, & Scout THE dog
2015 Hemisphere 282RK
2016 GMC 3500HD Duramax dually
1992 Goldwing Aspencade