It sounds like your main questions are regarding accounting. Therefore I recommend you talk to an accountant. Find someone (preferably by referral) who has experience in this area, get a free consultation, depending on your advice (and your state law) potentially hire them to incorporate a S-corp, C-corp, LLC, or whatever is appropriate. Ask them about liability, taxes, etc.

You don't need to have everything ironed out before you start, but if you start making money beyond couch change, you will probably want to talk to someone before the tax year ends.