How long do you hold a breeder to a puppy they “say” they’ve kept a puppy back in the litter for you.

I have a good breeder in mind that sent me pics of a puppy that I like. They said they going to hold it for me but I haven’t put a deposit down yet. They’ve been communicating very well with me. My only concern is how long do I have before I can put a deposit down and not lose my spot. I’m waiting for my tax refund that should come next month in order to have my deposit to secure my puppy. We’re talking approximately 4 weeks. My breeder said they’ll hold it for me until Feb 27th. I am scared I’m going to lose my spot and that this puppy won’t be available anymore. I really don’t want to lose it. I’m just trying to plan and make sure I have enough in case of emergencies with a new puppy.