I believe there are two parts to this question.
Part One: Call the Realtor from the sign.
Part Two: Submit an offer to purchase with the ability to assign the contract.
While I am not a Realtor, having never sold a single-family home in 37 years of commercial real estate, I believe the process is as simple as that for Realtors.
You did say this was a commercial property, but if it is a Realtor on the sign, it is likely a person who is more single-family orientated in the market place.
It might be well to have some good local advice from a good commercial real estate broker!
Onward and upward.... Rob Baird
Jun 14, 2011