
I wouldn't but some people do.
In my own breed people have traditionally never taken deposits, and some have only recently started doing so because of time wasters becoming more common, and finding that at collection time the new owners had changed their minds, got a puppy of another breed etc.
This leaves the breeder who may have been passing surplus enquiries on to other breeders in the position of having to advertise the pup, which with the specialist press will mean another couple of weeks before advert is printed, time which would be best spent in a pups new home.
I find taking a deposit means that new owner is sure they are getting their pup, and the breeder is more certain that the prospective buyer is serious.