237 has used two trailers in the past but we basically use the back of an Explorer to transport the robot these days. The Explorer is being used due to the courtesy of K.Shaw and Scott Shaw here on these forums.
The first trailer we used was my utility trailer. It was a "home built" single axle 5'x9' open utility trailer able to hold up to 2000lb. Had lights but no brakes. The down side with an open trailer is the elements and we basically limited this trailer to local demonstrations. I owned the trailer so I paid for the CT registration, $17 for two years. Here in CT we renew our registrations every two years. I also paid the property tax every year on it, $6 and change. The trailer had no insurance of it's own, it became insured as soon as it was hitched to an insured vehicle. The main vehicle we used to tow it was my father's S-10 Blazer.
There is no yearly inspection for personal trailers here in CT. The only expenses were the registration and property tax as mentioned above but these expenses will be different from state to state. Some insurance carriers may also require you to have insurance on them. Alot of this also depends on the size, type, and how the trailer is registered.
The other trailer we had was an 8' enclosed Haulmark that a parent (
Nick Reynolds) on the team had purchased. This trailer was fitted with cabinets and small machine tools and a portable generator so repairs could be made at competitions. He took care of the registration and other costs associated with it. This trailer was VERY heavy loaded down and some vehicles couldn't tow it easily. Nick's Aerostar had trouble with it. After Nick's son graduated he wasn't really active with the team. He passed away about three years ago (there's a thread on here about that) and the trailer was sold.
Both of these trailers were stored at the owners houses when not in use. Mine was under my deck while Nick's sat in the corner of his driveway.
Keep in mind that the tow vehicle or vehicles will have to be set up to tow the trailer that you chose. The hitch ball(s) will have to be the same size on the vehicle(s) to be towing it. The same goes for the wiring harness plug and electric brakes if required on the larger trailers. The tow vehicle(s) will have to be wired and have the brake controller mounted in them. The tongue height will also have to be taken into account and what class hitch needed. For large trailers being towed by an automatic vehicle will require an external transmission cooler to be added to the vehicle. Find out what vehicles you have available to tow with when deciding on a trailer. You could buy a 20' trailer and tow it behind a Surburban with no problems but if all you have available to tow it with is a Civic then you have a big problem and that 20' trailer isn't going anywhere! Also find out what paperwork, inspection and reqiurements are required in the state you live in. Remember they will also vary depending on the size, type, gross weight, manufacture* and the registration of the trailer.
*Some states have different registration requirements for a "home built" or "custom trailer" vs a premade one.