Unless your concrete it dead flat you will have hollows under the laminate glued down or not so you would still get sound.

I bought a residential building recently with a flat roof, the roof is around 1400 sq ft.

The market there is just so flat and dead.

That can be a flat fee (and a LOT less than 10% of the budget IMO).  

I know some want a percentage each month, but I'm just looking to do a flat one-time fee.

A flat pancake still has 2 sides.From a landlord perspective the risk is too great which is what the original poster is asking about and their tenant."

It appears, as Bloomberg's James Crombie notes, that point may be approaching as yield premiums for U.S. distressed debt hit a five-year high on March 25, according to Bank of America Merrill Lynch.BAML’s distressed debt index was at a spread of 2,483 basis points — the highest level since March 18, 2009 when it was at a spread of 2,609 basis points.Of course we have explained this won't end well...US corporates saw profit growth slow to almost zero last year and on an EBIT basis it has been flat for some time now.

It worked out that it was a panel discussion on rentals and SMEs for different areas.  

Some houses might face a busy street, have a flat yard versus sloping, next to power lines, etc.

You have to check the loan documents also because in addition to a pre-pay penalty you mentioned there might be an assumption fee to assume the loan which is usually around 1 percent or a flat fee.Sometimes the lender has when the loan gets closer to maturity the pre-payment penalty goes away or keeps getting reduced to a smaller amount.You will need at least tens of thousands for due diligence and closing costs.