A cheap (usually free) and easy swarm trap can be made using a copy paper box:
One or two standard deep frames will fit just perfectly into the box from corner to corner. Insert the frame(s), drop in a cotton swab with some lemon grass extract, and put the lid on. The lemon grass extract acts as a swarm attractant. If you ever come across a swarm, you’ll immediately notice a lemon smell. The lemongrass extract mimics that and attracts scout bees that are looking for a new home for their swarm. You can purchase lemongrass essential oil at Amazon.com for around $6. I usually run duct tape all the way around the lid to keep it from blowing off and to contain the bees when I move them. Pop in one of the handle holes for an entrance and you’re set to go. I usually put these under over hangs in old barns or on porches where they won’t get wet. If its someplace out in the open weather I’ll use a easy 5-frame nuc as a trap. I caught 2 swarms last year using one of these boxes on my front porch, and this was before I had bees so they weren’t from my hives! The video below shows me moving a swarm caught in the free box into an easy 5-frame nuc.