The most important thing you need to understand when considering a pet is whether you will be forced to part with your pet and thus make it a shelter dog for someone else to adopt. In additon to the ovious horror of parting with what amoutns to a family member, if you give up a pet, the future life of your pet is unknown to you. The two most common reasons that people give up their pets is because they move to a location that doesn't allow pets, or expenses of caring for the pet exceed your resources. Only you can evaluate whether your residence will accept your pet forever, but expenses, or at least a reasonable range of expected expenses, are forseeable.
TheSimpleDollar has a detailed page on estimating the costs of obtaining a cat or dog, and estimates of the veterinary care, food, training, and other expenses over time. Their examples do not include the Chuhuahua breed, so look for other small dogs for examples. It's hard to find a link to pet costs from the main page or their search engine, so save this link. If you've never had a pet before, you should estimate the costs of taking care of one before you committ.Want a Chihuahua or other fine pet or companion? Check these links for the purebred or other dog of your choice. You can't beat the price, and you're doing a good deed for the dog and the pet community.
http://public.homeagain.com/ is the largest pet tracking implated chip resource.
http://www.dentalone-md.com/guide-to-dental-care-for-pets/ is a non-commercial web page, hosted on a commercial web site but is an information page with many informational links helpful in pet dental care but no commercial links.