Welcome GotBetta :)
I strongly recommend reading the stickies throughout these forums as they can answer the majority of your questions in great depth.
In particular the basics: http://www.bettafish.com/showthread.php?t=20058
I highlight for you something of concern to me from P3's guide also http://www.bettafish.com/showthread.php?t=64078;
First thing’s first, ask yourself these questions:
- Can I afford spending at least $40+ on tank/heaters/supplies?
- Am I willing to make possibly very frequent water changes, depending on my tank size?
- Am I ready for a creature that can live to up to five years?
- If I have to go on a trip, etc, can I get someone to look after my fish?
- Do I know the very basic info about a betta? (Research!)
- Am I willing to get the minimum size tank and the needed supplies for my pet?
If no to any of these, do not get a betta. They deserve the care and respect of any other pet, not unlike a dog or cat. If you are unable to get what you need, then wait. You wouldn’t get a horse without a big enough place to put it, right? Or a dog without food, right? Same for a betta!
Not to put you off or be mean mate, but a basic Betta setup is definitely required, and a Heater is crucial and necessary key element. Quite honestly the bare minimum to have a Betta is a tank, a heater, water conditioner and food.
Whilst it may seem not necessary to you at this juncture, overnight temperates can drop drastically as Micho said, not to mention in 6 months time it will be Winter. Currently this means your Betta's tank temperature could fluctuate from high 80s to low 60s causing undue stress and eventually most likely causing disease and further issues and expenses such as medicines to keep your Betta alive.
Think of fluctuating temperatures as you would on yourself, it would give you a cold or the flu.
There are many various heaters out there from cheap to modest to expensive. It is certainly not something you should scrimp out on.
If money is that tight currently, I strongly recommend saving for now until you have a complete basic Betta setup. Once you have achieved the funds required, put it all together and procure your Betta :)
I don't mean to be mean here, I'm just very concerned lately for the welfare of Bettas! Particularly when heaters are relatively cheap.