I've sold at some smaller pop up events and local anime conventions, as well as two out of state cons: I've been doing this for over seven years now. It's a great opportunity and learning experience. Competition is very fierce but I wish you the best on your creative journey: Key things to consider BEFORE you start, based off my experiences:
What kinds of styles, themes and aesthetic are you going for?
What types of items do you plan on selling?
Target Audience/demographic: Who do you expect to sell to? I love making cute, colorful creations. Examples are chibi animals and/or food. my stuff does well with young crowd and LGBTQIA+ community.
Register your business through the IRS. Disclaimer: This part is definitely not my strong suit. We have a family accountant to help guide me through these steps. I started out just selling in my home state. For every state you plan to sell at, especially for a big con, you need to register your business for those states. Tax reasons
Record business investments, keep track of sales, profits and losses. For reporting/filing taxes to the IRS. Again with the disclaimer: Not my strong suit dealing with IRS or filling out paperwork
Research the cons/events beforehand, especially if not local. This includes location, what the con has to offer (programs, panels, guests, etc.)
Having a well -put -together, powerful, and eye catching display will attract more people. Part of marketing your brand.
I still have A LOT more to say regarding cons, lol, both as attendee and seller. Feel free to message me :). ALSO: STAY HYDRATED, FEED YOURSELF ENOUGH, STRETCH/ WALK AROUND PERIODICALLY.