Hy JakeCard, if you're looking for an old commercial semi trailer, you'll have to convert your trucks brakes to full air brakes to be compatable. A lot of older trailers have vacuum brakes with a "hand valve" in the truck to actuate them [they do not come on with the truck brakes]. The modern gooseneck fifth wheel trailers will have a choice in brakes, some will be electric brakes, which would be fairly simple to fit a controller into your truck for, but those trailers are going to be expensive. As Hotrod Lincoln said, there are legal considerations when operating a rig like that, if you were thinking of insuring it as an antique/special interest/collector vehicle, then I would contact your insurer and see if that is even possible for your truck hauling a load. Hope that helps.
