Get at least a 18 footer, steel deck, 4 ft dove tail for lower loading angles, make sure it is built with at least 4 inch channel DO NOT GET ONE MADE WITH ANGLE IRON, IT WILL TWIST. Make sure it has a dual c channel frame, the top one just for the metal deck and a bottom one for the main frame, some main frames only go back half way, try to get one that goes all the way to the back or aleast past the axles. Get one with reccessed light so you dont take them out on corners, get reccessed d rings for tie downs, get a bull dog hitch, at least one axle brake. 2 3500lb axles will work with an open trailer since the trailer will only weigh 1500lb. get c channel ramps for less bowing while loading. try and get one that is painted underneith also for rust protection. Get an extra long tongue for room to mount a tool box.
JMHO
Greg