I am planning to make an offer on a home, but there are issues with the concrete floor in the garage and adjacent work room. About 2/3 of the garage floor and the enitre work room floor have sunk from 0" to 3"+. Does anyone know what it would cost per cubic yard to have the existing slab removed, underlying soil properly compacted, and new slab prepped, poured and finished? Garage is 21' x 28'; work room is 12' x 12'.

I'd love to give you a number but labor and concrete vary so much it would not be very accurate. A virgin slab would run you around $7500. You really will be better off to hit the yellow pages and get 3 bids from contracts in your area who would actually be able to do this work. It will not be cheap and your seller will likely tell you the subsidence was obvious and already factored into his selling price.