Welcome to the forum PZC.
You can indeed keep Betta splendens with minimal pre-arrangement of equipment but it will mean frequent large water changes to keep the fish healthy. Betta breeders are known to never filter their tanks and to control the water chemistry through the use of frequent large water changes. It makes their life a bit easier but is probably not the best situation for their fish. As hobbyists, we mostly do not favor such intense care for our fish so we establish a decent environment that can accommodate them well instead. That will mean setting up at least a 2.5 gallon tank for your future betta with a cycled filter on it. I favor large tanks for my own bettas but I house mine with lots of other fish that really are the reason for the big tank. I have 26 running tanks as of today and cannot afford the time to care for a single betta in a small tank. That is my situation, not yours.
To get the best response from a new betta, I am going to suggest that you get something between a 2.5 and a 5 gallon tank with a filter and a small heater. That filter should then be cycled using a fishless method until it is ready to support your future fish. I have a link to fishless cycling in my signature area because it is a subject that comes up quite regularly. After you have cycled your tank's filter, please feel free to get any mature Betta that you like. It is important that you really like the fish you get because you will need to care for it for about a 5 year life span. It is not as long as a puppy but definitely a long term commitment. My own male lives in my 45 gallon endler tank with about 75 endlers. He is around 5 years in my care and was a mature adult when I got him. He has been in a few different tanks during his lifetime and is now expected to earn his keep by controlling my endler population. I must say he is a total failure in that job but I like him nonetheless. He works hard to get his daily exercise in a tank large enough to give him lots of swimming room with enough water flows to give the endlers a bit of a workout. In many ways I think he is stronger than the average Betta splendens since I have refused to baby him with low flows and special foods.
) I am new here! I used to have gold fish back when when i was 6 years old! 10 years later, I want fish again! My friend who used to own a lot of fish (mostly betta fish) invited me here if I had any questions or needed any info on taking care of fish. I'm thinking about buying betta fish from Wal-Mart (it's the only place in my local area that sells fish) but first I'm trying to study the care and needs of a betta fish! 
