Welcome to the forum.
I tend to be a bit blunt, so let me know if I come off as too harsh. It's not like every betta owner has to dedicate a part of his or her livingroom to bettas like I did. So I know I went over board a bit in terms of fish care. But I think you fell for the "Bettas are easy fish" trap like a lot of new fish owners.
I understand that a lot of fish owners have limited space for their fish. I strated with bettas when I was on campus in a dorm room, so I didn't have my fish in anything larger than a gallon until I was in my own apartment. If you only have room for a small set up, then 1 gallon is the minimum you can safely keep a tropical fish. Bettas need their water to be 78-80 degrees. It isn't possible to heat 1/2 gallon properly, which is why Sweeda88 warned you that your betta kit is not proper. If you do go with a 1 gallon set up, ZooMed and Hydor both make good small tank heaters and both are pretty cheap.
Even if you do figure out a way to keep the water temp constant without a heater, you have to keep the water clean. A 1/2 gallon set up would need 100% water changes every other day. Not only is that a hassle for the fish owner, but that is stressful for the fish. I had a 1 gallon filtered set up that required 2 50% and 1 100% water changes a week. The 50% water changes were quick and my fish were stressed once a week compared to every other day. A lot of members on the forum will suggest 2.5-3 gallons because those set ups only need 1 50% and 1 100% water change a week. More water means less work to maintain the tank. :)
If you don't have enough plugs in your kitchen for a heater (filter is optional if you do enough water changes), then you can't have your fish in your kitchen. If your set up isn't 1 gallon (which is the smallest set up that can handle a heater and/or filter), then you have to upgrade the size. I know your friend was using the fish as a center piece, but that doesn't mean Betta fish are decoration. They have basic needs that have to be met for the sake of the fish.
I hope this helps you with your new fish. I hate when people fall for Betta fish myths. The longer you are on this site, then more you will realize most pet store workers don't know what they are taking about. :)