6 weeks is waay too young. Especially for a toy puppy. It sounds like the breeder you're dealing with just wants to sell the puppy as soon as legally possible. The deposit thing, and how you sound soo unsure of this breeder, is also not a good sign. Have you met the breeder in person or spoken extensively with them on the phone/e-mail? Have you met both of the parents to be SURE of their physical and temperamental soundness (along with socialization, good care, etc)? If you're buying this puppy from an on-line breeder, RUN. I assume you are paying a LOT for a Chi puppy, you should definitely put that money into a reputable local breeder who you can meet in person and feel more comfortable with. Just the fact that you don't seem willing to talk about how young the puppies are with this breeder gives me the feeling that you aren't comfortable with them

Its sooo sad how badly people are betrayed buying puppies from the internet and pet stores. Seriously, you should consider finding a really good breeder that you can meet in-person, this dog is an investment of your time, money, and love, and you should be VERY picky about where your pups come from. Generally, NO good breeder will sell pups before 8 weeks of age. Also... since you are worried about the Boxer, think about this thoroughly. Do you think you can care for TWO puppies at once? That means, potty-training, Obedience training, crate training, dealing with chewing and behaviors for two pups at once. Boxers are a huge handful, and they're very very hyper and outgoing pups. One problem could be the Boxer puppy playing too rough with the tiny Chi puppy and hurting him/her. Realize that you might have to deal with keeping the two seperate most of the time.... definitely consider waiting until your Boxer puppy is 12+ months old and has been through Obedience training and has passed their puppy stage, and between now and then you'll have plenty of time to find the PERFECT Chi breeder that you're confident they have healthy, sound, wonderful puppies/parents and are a fantastic breeder

DONT feel rushed into buying a puppy... you will have this puppy for possibly 15+ years!! Chihuahuas have been known to live very long and happy lives, and you'll have 100% less health and behavior problems down the line if you buy a puppy from a reputable breeder that you know and trust! Check http://www.akc.org for a list of reputable Chihuahua breeders, also ask your state/area Chi Club for breeder references. Buying from a good breeder is completely worth it, you also do NOT want to support puppy mills, Backyard Breeders, and brokers who neglect and over-breed dogs by buying from pet stores, internet broker sites, etc.