Bradford Marine/Brokerage Sales

I would suggest asking them to get an accurate and definitive answer. It may be true or false or may be just something told to one owner who has abused the privilege.

Is that a common practice, free moorage for brokerage vessels? If so, is the goal that a percent of new owners will stay at that facility?
I get, from the brokers side, that negotiating free moorage will give them a marketable advantage in obtaining listings.
What is in it for the marina?

Has been somewhat common where brokerages and marinas are one and the same. Broker gains advantage in getting listings and that is the purpose. Marina can gain some work in preparing the boat and then maintaining it through the process. Bradford also had the advantage of being undercover.

Then the negative. With dock space in demand, it gets expensive and many owners have really abused it and used it for free storage when their seriousness in selling turned out to be questionable. Time limits become fights with the argument that it's the broker's fault it's still there.

I had a friend who owned a dealership on the lake and did it briefly copying a competitor and he stopped it very quickly.

Sort of what I was thinking. There seem to be way to many owners who would take advantage of this by listing with no intention of selling in order to get free moorage.
I think, if the marina were to do this for brokerage boats, they should investigate the seriousness of the sale. Anyone can list a boat with an inflated, I'll sell if someone comes along and pays way over market, price.

Another benefit to the marina may be foot traffic. Brokerage open houses and showings do create traffic. So if the marina can sell some coffee or rent a SUP to the foot traffic and make the environment something desirable to potential buyers there may be some up side. Especially, as you say, if the marina is not at capacity.