Lessons are expensive sometimes. Been there, done that. A $500 loss is nothing compared to the vet costs you may/most likely incur with an unhealthy pup. Go find a reputable breeder. I personally will not pay a deposit before I know which puppy I will get. Makes for less options in finding a breeder but a deposit makes me nervous.
If breeders are so keen on deposits early on, to me that means that they are not sure if they can place all pups. Deja's breeder doesn't do deposits. If I were to cancel a pup, he would have people lined up or train the pup himself until the pup finds a home.
If I were a breeder I would be happy when people change their mind (to prevent a miserable home for my pup), rather than insisting they take the pup by holding on to the deposit.
Exactly this - I would rather walk away having lost a few hundred dollars than take the puppy just because and either be unhappy with my choice, or faced with years of managing a dog with health issues. There is a chance the puppy will be absolutely fine, with nothing out of the norm - and grow to be a healthy dog you will enjoy for many years. But without the support of a breeder, I wouldn't chance it. Every puppy is a gamble, but without a breeder you trust to turn to if something goes awry, its just not worth it, IMO.
I do not ask for a deposit for my puppies until they are temperament tested and chosen for their families. I want people to get the puppy because they WANT the puppy, not because they don't want to lose their deposit.
You can absolutely ask for a refund - word the message politely, maybe something along the lines of "Hi [Insert name here], thank you so much for all of your help thus far, however as I have been researching more and more, I sense that I may have been hasty in placing a deposit on a puppy. I feel like I need to do a bit more research in order to ensure I get the best puppy for me and so I can be the best home for that puppy. I hope you understand, I really do want to ensure a successful placement, as this is what would be best for all involved. Would it be possible to have my deposit refunded? I do know when we talked that you had indicated it was non-refundable, however I am hoping we can work things out."
If the breeder declines, then you will have to choose what will work best for your situation. Best of luck and please do post an update