I'm not a breeder but do want to say, definitely watch out for scams, there tends to be alot of email "I wanna buy a puppy" scams,
You can always require a 'deposit', some type of contract, regarding return or non return of deposit.
Frankly, I think selling puppies especially since your new to this, to people who can't come meet you/dogs in person, unless you know them, get references, (espec VET references), etc, it can be a crapshoot. People lie, people will say anything sometimes to get a puppy
I'd try to advertise locally, get references, ESPEC vet, and call them !! ask what happened to their past pets, just letting people "ramble" you can sometimes get a feel for them