It's hard to know if the new homeowner will appreciate the system- some might, some will want it to be gone, so they can build a new one that reflects their immense knowledge of technology and making its operation difficult. Ask the existing homeowner if they'll be selling anything before they go and if so, offer to find current value for the components so they can be sold at the same time. Then, be available to remove it and make your name and service offerings known during the sale.

The daughter of one of my clients moved back to the area and when they found a house, the Russound conrol unit was gone, but they left the keypads. It was there when they looked at the house and they had photos of it. I told them to ask the realtor about it and he admitted that it was there without saying "I took it" and said he'd return what was there. He left a low end Pioneer AVR with dented case and an 'Open box' sticker from Best Buy.