My foundation is crumbling and needs to be replaced, but we won't have the money do so for many years. Because of this the floors throughout the first floor are wavy, lots of valleys, walls are separating from built-in fixtures, etc.

On the second floor the master bedroom is still old wide plank wood flooring, they did a piece on "fixing" gaps in this style of flooring by putting rope in the gaps.

The hallway has newer flooring over it, there is about a 3/8" lip between it and the bedroom floor, so I think I can add material.

The floor will actually sink in in certain spots when you step on it, and it appears to curve down towards one wall.

We really need a solid level-ish floor in this room as we are converting it to an office, if you sit in a wheeled chair now, you roll towards the door. Do you have any suggestions for leveling this floor that could be removed later when the foundation is fixed?

I tried to include pictures but it won't take them.

I've heard of self leveling compound, then may put some type of finished plywood or laminate down? I'm not sure what would go on top of it, carpet would be nice!