AZ: No, you don't have to form a corporation. There may be reasons to do so, depending on how much money you will make, what state you live in, and other factors, but those are the same factors that apply to forming any single-person corporation (e.g. lawyers, doctors, etc.). Unless your planning on doing something to cause you to need to hide behind a corporate liability shield (does this even work for S/C corps?), you don't need it to start out. Give an accountant a couple hundred for a consult to tell you the pros/cons.
Additionally, corps have to pay professional exchange fees, which can amount to hundreds of dollars a month, depending on what you trade and whether you want to have a backup platform (for which you must pay a second set of exchange fees).
Additionally, corps have to pay professional exchange fees, which can amount to hundreds of dollars a month, depending on what you trade and whether you want to have a backup platform (for which you must pay a second set of exchange fees).