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Walmart should not be selling live animals. They have a terrible reputation for their fish sections and are infamous on /r/aquariums. If you are interested in owning a betta there are many myths to dispel. First off they need a minimum of 2.5 gallons, 10g is much easier to manage for a beginning fish keeper. They are tropical fish and require a heater. ALL fish need a filter and NO fish should live in jars/bowls/vases. They will not live on plant roots; they require a balanced diet. They do live in rice paddies but rice paddies, while shallow, are vast and naturally filtered. Just because they are hardy enough to survive the shitty conditions many people put them in does not mean they should live in them. Head over to /r/aquariums or /r/bettafish for information about proper husbandry, the essential nitrogen cycle, and setting up a tank.

Also worth noting: if you feel like being a vigilante and changing their water make sure to condition it. And more food = more waste which makes their sad little cups more toxic. If you go around feeding them you aren’t really doing them much of a favor. It can be hard to resist “saving” one (I don’t even visit my local walmart’s aquatic area because it breaks my heart) but buying a betta from them only encourages them to stock more. If you are interested visit a locally owned fish store and always research before you buy.

Edit: also, barring illness or poor genetics bettas should live 5-7 years when properly cared for.

Edit 2: Here’s a pic of my betta and his current home. I’m honestly not even a “betta” person; this fish was given to us as a present for the kids. I’m much more of a predatory oddball lover but I feel obligated to provide good care because it’s a living creature. He’ll live out his life sassily and comfortable until old age gets him.