I personally would say, "Call me once you get a nice setup that is predator proof for you remaining duck, and I'll sell you a few more."
A gal wanted to buy a few hens from me, and she was smart enough to ask about her coop setup before bringing them home. It wasn't safe. An open air coop, and no fencing or anything around it in the city. A coon, skunk or any critter..dog...big tom cat would have them for a snack.
I was very nice though, explaining that her setup wasn't really safe yet, and once she got things squared away, to give me a call.