I'm way too far away to be interested in them, but I just wanted to say that unless you actually know for a fact the male was neutered it's best not to assume he is, it's not a common thing. Chins can be together for years before producing any kits if the conditions aren't right. Sometimes all it takes is a change of environment (new home or even new area of the room), better food, less stress, etc can all suddenly change things so the chins decided now is a good time to mate. I had a pair when I was a kid that I was told was a male/male bonded pair, they were together for 3 or 4 years so we never questioned it, then one morning I woke to find two little kits in the cage. Luckily I happened to already have a spare cage that was kit safe to move the mother and kits into.
Also keep in mind that the gestation period of chins is 111 days, and they don't always show. So I would make sure who ever buys them knows that the female could be pregnant since she lives with a male. I've seen way too often people being surprised and unprepared for kits after being told the male was neutered or sterile because they hadn't had any kits yet.