Class A
The Class A is the largest and often most luxurious of motorhomes available. Most models offer complete self-containment, with on-board generator, large water and holding tanks, big batteries and a generous propane supply. Such features also make these units especially good for "dry" camping (without hookups), even for extended periods.
AVG Weight: 13,000 to 30,000 pounds
AVG Length: 30 to 40 feet in overall length
AVG Height: 10 feet high

Class C
Class C motorhomes are built on RV cutaway van chassis that are designed expressly for this purpose. They retain the cab section of the van with the driver and passenger doors, which are definitely convenient. To most drivers, Class C motorhomes "feel" more natural to drive than Class A's, especially the first time they are driven.
AVG Weight: 10,000 to 12,000 pound gross vehicle weight
AVG Length: 20 to 25 feet in length
AVG Height: about 10 feet high

Class B (Camping Van Conversion)
Camping van conversions, also known as Class B motorhomes, come in a number of configurations, the smallest and least expensive being the plain van conversion (street van) that retains the original van dimensions but features a raised roof, usually fiberglass, and offers full headroom. These models include abbreviated motorhome-style accommodations, such as a small galley and a portable toilet. Camping vans using today's extended-van chassis feature some very innovative packaging and floorplans with expanded amenities, including full self-containment and quite acceptable livability for two adults and occasionally one or two small children.
AVG Weight: 6,000 to 8,000 lbs
AVG Length: 17 to 19 feet
AVG Height: 7 to 8 feet

Travel Trailers
Trailers in the under-4000-pound category range in size from compact 13-foot models up to those measuring approximately 22 feet. The larger units are suitable for extended use, while the smaller units make great weekenders. The 18-foot and larger models offer full bathroom facilities, including a separate shower and a fully equipped galley. Living room and dining-area space and furniture are governed in large part by the overall size of the unit, with the more elaborate layouts being found toward the upper limits in size, class, price and weight. The larger models in this size class require some serious consideration of the tow vehicle selected.
AVG Length: 10 to 35 feet

Fifth-wheel Trailers
For anyone seeking maximum living space for a given trailer length, the fifth-wheel trailer category is the place to look. "Fivers," as they are sometimes called, pretty much have become the RV of choice for most full-time RVers. Models are available with a wide range of typical RV appliances and some not so typical, such as a built-in washer and dryer. Slide-out room extensions are common with the large, high-end models offering triple slide-outs on both sides of the living room area, plus one in the bedroom. These slide-outs greatly expand the available living space and increase the total trailer weight. Most of the large fifth-wheel units require, at the very least, a one-ton pickup truck as the tow vehicle. It is extremely important to match the weight of a fifth-wheel trailer to a truck of adequate towing capacity.

Folding Camping Trailers (Tent Trailers)
The folding trailer or tent trailer is a good place to start. These lightweights offer lots of sleeping capacity: usually a pair of double beds, plus the dinette converts into a double bed in most models. Since most tent trailers utilize canvas for side-wall construction, they offer many of the advantages of sleeping in a tent -- you can still hear the birds or the wind while being protected from most of the elements. Most models feature minimum cooking facilities, with a two- or three-burner stove, a sink and an ice box, or an optional small refrigerator. The living area is quite pleasant, offering an open and spacious feeling because of the large, roll-up vinyl windows in the canvas sides. Setup requires about 10 or 15 minutes. Most can be towed with just about any size smaller car or downsized SUV, minivan or truck.

Toy Hauler
A Toy Hauler is specifically designed for those who want all the convenience of a trailer home and want to take their toys with them. So if you have ATVs, motorcycles, or even a race car you can just put them in the back and go. Living space will be sacrificed in many of these units however, if bringing along the toys is mandatory, then this is a good compromise.