To avoid scams, know that French Bulldog puppies are expensive as they are difficult and complicated (sometimes) to produce and care for as they tend to have smaller litters and require surgical intervention at birth (C-sections).  Most start at $3000-4000.  Anything less and you might be getting a substandard example of the breed.  The expense climbs as the rarer colors are displayed or the DNA shows they carry desirable traits to pass on for rarer colors and good genetic disposition.  

Be sure that you are getting a quality pup by checking the pedigree to check for inbreeding (breeders call it "line breeding"...but it is inbreeding and that can produce disastrous results).  

If you are putting down a deposit or making a payment make sure it is transferred in such a manner that there is a paper trail or a  wire transfer bank to bank.

Insist upon seeing the dog on live video and take screen shots of the pup to ensure you are getting the right pup.  Do not buy sight unseen!

Be sure there is a contract that is fair to both parties.  Hand shake deals for expensive dogs is risky business.