Hi tmacarthurrf14,
Welcome to the HVAC Group!
What you want to do is a very good idea for a quality serviceman. I carry both a "B" tank acetylene and an oxygen/acetylene rig on my service truck and use each frequently depending on the size of the job.
You can buy these used, however it is best to get one of each with the regulators, hoses, and tips new because of working quality and safety. The bottles when empty you can exchange at the HVAC supply store for full ones but I always carry an extra full of each on my service truck in case I run low.
These tanks or cylinders are supplied in convenient sizes so that they are portable and we can carry them where we need to work on our units. Oxygen/aceletene and aceletene alone do an excellent job with torches of proper design and size and regulators to control the volume and pressure. I like the acetylene over the butane because it puts out much more heat, therefore you can cover a wider range of overall jobs. With the air-acetylene swirljet you can produce an effective 4200F.
The oxyacetylene flame has a peak temperature of about 6000F, and is known to be the highest temperature gas flame produced. The highest temperature occurs just off the end of the inner cone of the flame. Be careful with the oxygen/acetylene torch because it is easy to overheat, however the more practice that you have the more familiar you become with your tools. Always keep the torch head moving.
A cutting torch is a handle with a lever, when the proper temperature (high) is reached, you press the lever for extra oxygen to blow a hole and you move the torch head the direction which you want to cut.
Good Luck with your studies!