Someone in this situation rarely does a C-Corp (expensive, double taxation, no need to obtain venture capital, Section 1202 stock not going to be an issue likely).
An S-Corp on the other hand tends to offer some self-employment tax savings and is a pass-through entity, so no double-taxation (start with an LLC through your state, then elect S-Corp status using Form 2553 at the federal level). As a personal service S-Corp, which you likely would be, Congress is currently looking to plug the employment tax savings loophole by year end. Before this (the new bill), doctors, lawyers, consultants, me, and others have been paying taxes on part of our earnings subject to employment taxes, while the other part we get to take subject only to income taxes.
If you don't do one of the above, you can report your earnings on Schedule C of your Form 1040. All of your earnings will be subject to self-employment tax on top of regular income tax. If you are in a higher tax bracket to begin with, it means about half of your earnings can go to taxes (self-employment tax is 15.3% in general).
Let me know if there is something more I can do to clarify. I might try an S-Corp if I were you, especially depending on your business, but this does sound like a situation where, once Congress acts and you have a personal service S-Corp, you might as well just stay on Schedule C of your 1040.
Thank you for your question.
I started my S-Corp for $75 (state filing fee: articles of organization).
If you do an S-Corp, you have to pay yourself wages, otherwise you would pay no employment / self-employment taxes at all (the IRS really frowns on this). It's common for CPA's to suggest ratios for your earnings (60% wages, 40% dividends, for example). The dividends are subject to only income tax, while you'll pay the 15.3% employee/employer portion for the wages.
The dividends are supposed to represent earnings from a growing equitable company. You really don't have that here. The salary, however, must be "reasonable" as compared to that of another doing the same work, and getting paid a similar amount (see what others get paid for your work, and you'll find it's almost all going to be salary I bet too...).
Honestly, I'm thinking Schedule C might be better, or at least more conservative.
Other than incur expenses for business purposes, no.
Schedule C is the default form for any sole proprietor that does not incorporate. No 'business' needs to be created (you've already done that).