A sauna trailer is a cabin built on a road-legal chassis, so it can be towed to a lake, a race, a festival or a friend's yard. Most are wood fired, most are sold as businesses rather than as garden furniture, and the interesting parts of the purchase have nothing to do with saunas.
What you are actually buying
A small timber building on a braked or unbraked trailer, usually with a wood stove and a flue that drops or hinges for travel, a changing vestibule and sometimes a cold plunge on the tongue. The sauna half is a conventional cabin. The trailer half is where the weight, the axle rating and the road legality live.
Towing and registration
It is a trailer, so it needs a title and registration in most states, lights, a rated coupling and a tow vehicle that can pull the loaded weight. Check the gross weight rating against your vehicle's towing capacity rather than the empty weight, because a cabin full of timber, stove and stones is heavier than it looks.
The stove on the move
A wood stove on a trailer needs the flue secured or removed for travel, the firebox cold and empty before moving, and the same clearances as any solid fuel appliance when it is in use. Never travel with a lit or recently lit stove. Where you park it also matters: the same fire separation applies in a field as in a yard.
Whether it makes sense for you
As a private purchase it is expensive for something you will tow a handful of times, and a fixed cabin plus a tent for travel usually costs less and works better. As a business it is a proven format: mobile saunas rent well at events, races and lakesides, and that is what most of the market is built for.
Questions people ask about sauna trailer
Do you need to register a sauna trailer?
In most states yes, as a trailer: title, registration, lights and a rated coupling. Check the loaded weight against your vehicle's towing capacity.
Can you tow it with the stove lit?
No. The firebox should be cold and empty and the flue secured or removed before moving.
Is it worth it privately?
Rarely. A fixed cabin plus a tent for travel usually costs less and works better. The format earns its keep as a rental business.