There are many things to consider when buying a rabbit: who the rabbit is for; how many you want; how old you would like it to be; the breed and gender; the place to buy it; who your vet will be; and how the rabbit is going to be housed. Price, though important, should be the least of your concerns.
Rabbits do not often make good pets for children. They do not like the handling that little kids often use on cute fuzzy animals. If you are buying a rabbit for a child, you will want a larger, more temperamental breed. Smaller breeds tend to be high strung, nervous, and less affectionate. Also if the rabbit is for a child, remember that a rabbit should be a PERMANENT COMMITMENT, not just a toy for the child to play with for a week or so and then decide to get rid of. Many gift rabbits end up either in animal shelters or rabbit rescues because the child for whom they were bought ends up getting bored. Even worse, some of these "forgotten" rabbits are left to starve and die in their cages. So if you are buying the rabbit for a child, make sure that the child is responsible, knowledgeable about basic rabbit care, and is prepared to keep the rabbit for a long time.
Rabbits can get lonely sometimes even when their owners are around most of the time. (After all, no one can be by their rabbit 24/7.) Some people buy multiple rabbits in order to solve this problem. All the information on owning multiple rabbits can be found on the multiple rabbits page.
Most people like to start fresh with a baby bunny. Rabbits sold at pet stores have often been weaned too early; they are sold at the age of 4-6 weeks and sometimes even younger. This can actually be a health risk to the bunny and it may even die. You may want to buy a rabbit that is slightly older; breeders, rabbit rescues, animal shelters, and some pet stores will have older rabbits available. Or, you may choose to have a baby rabbit "reserved" at a pet store for a week or so; this way, if the baby rabbit remains healthy during the "reserve" period, you will be more likely to have selected a healthy baby.
Information on rabbit breeds is completely covered under other rabbit sites, which can be found on the page of commercial rabbit site links and the page of bunny lovers' links. It is important to consider breeds because breeds play a large role in the size and personality of rabbits. Long-haired breeds require extra grooming. Certain breeds have personalities better suited for children, and certain breeds are better when you want to put your rabbit in shows.
Gender is an important factor if you are planning on breeding your rabbits or owning more than one rabbit. (If you own unspayed male and female rabbits, you will ultimately end up with baby bunnies.) Or, you may just prefer to know the gender of your rabbit ahead of time. The DebMark Rabbit Education Resource has a page on the sexing of baby bunnies which helped me to successfully determine the gender of Mopsey when she was only 6 weeks old and I HIGHLY recommend it.
There are many places to buy rabbits. Around Easter time, they are sold very young and very cheap at county fairs and open markets. These rabbits are sold too young and there is a high risk of running into medical problems because of this (and also because you do not know how reputable the seller is).
Rabbits are most commonly sold at pet stores. Be sure that you are buying a rabbit from a reputable, clean store. Make sure that the store owner has some knowledge about owning rabbits and how to take care of them. Feel free to ask questions, or ask for a vet recommendation. Be sure that the store has a return policy if you find that your rabbit falls ill within the first few days that you own it. Bear in mind that pet store bunnies are not often purebreds; if you want a showbunny then you are better off buying from a breeder.
Breeders sell rabbits that can be sold in shows; some also sell mixed breed rabbits. Make sure that the breeder is knowledgeable about different breeds. (Some "breeders" merely mate any rabbits and are not true breeders, who know all about the different types of rabbits.) A good breeder should be able to tell you the gender of the baby rabbit as well as feeding, housing, and grooming info. Ask for a vet recommendation.
Rabbit rescues are privately owned facilities where purebred and mixed breeds rabbit of any size and age can be purchased or even adopted for free. Rabbit rescue owners are often true-blue bunny lovers who can tell you everything you want to know about owning a pet rabbit. The only thing they may not be able to tell you is a rabbit's medical history, especially if they rescued a rabbit "off the street." Check the Internet or join a rabbit discussion group to find rabbit rescues in your area.
Animal shelters also have abandoned rabbits of all sizes and breeds. Rabbits from shelters are most likely up for free, but again there is the risk of not knowing the rabbit's medical history. Animal shelters are listed in the phone book and on the Internet.
If you do not already have a "family vet," ask your friends for a recommendation or ask the pet store owner/shelter worker/breeder for a recommendation when you buy/adopt your rabbit. You can always look up vets on the Internet or in the phone book as well.
NOTE: not all vets are experienced in small animals. A vet who is excellent in caring for cats, dogs, and/or livestock may not be as good when caring for smaller animals. When choosing a vet, do not be afraid to ask him/her if he/she is experienced with smaller animals such as rabbits.
Information on housing your rabbit(s) can be found on the Housing, Bedding, and Cleaning page.
Rabbits, their houses, their bedding, etc. is priced differently at every store. Rabbits themselves are free when you adopt them from most animal shelters or rescues. Breeders will charge more for purebred rabbits than stores will charge for mixed breed rabbits. On average, a pet store will charge $20-$40 for a baby mixed breed rabbit; full grown rabbits will cost a bit more. Baby rabbits that are sold at fairs will cost only about $10-$20.