I bought a groupon for $89. It was for cleaning of unlimited vents and unlimited cold air returns.
When the "technician" showed up he was in his personal vehicle, not a company vehicle. I have no idea where he kept his tools or supplies.
The first thing he did was "check" my furnace. Then proceeded to tell me he would not clean out my vents unless I bought $400 worth of other services from him. I told him no, my furnace works fine and he just left.