It depends on the size/ cost of the frag swap.
If it's free to sell/ buy, like at a LFS or backyard swap- just power, possibly limited tables and/or limited space in a community frag tank (use at your own risk). May or may not have food- tacos or pizza or potluck where everyone contributes.
If your promoting something large, charging admission at door/ charging for sellers booth... good luck. If you been in the hobby since '11 you may know some of the history of SCMAS, Kevin Adams and MAX. I never went to a MAX show but did sell as a hobbyist at RAP and attended several as a member. It was a blast, I think it was $150 for half of a table which included an Aqua Pod tank you got to keep. I got to meet a lot of people face to face after knowing them online. I got to move a lot of overgrowth and made a bunch of people happy. Set up Friday, sell Sat, Sun. They provided Catalina water as well as power cords, linens and chairs. Security overnight, there were no issues. There were early entry door prizes, the shows were well promoted, lots of parking.