Years ago there was a published online dingy towing guide magazine format that was free. That's gone now. Now there's one with a similar format behind a pay wall or at least I think it's a pay wall in that you have to join to access the towing guides and I don't want to join:
Towing Guides
If you are able to find a free online comprehensive list of 4-down towables, please let us know here with a link. Note that a front wheel drive vehicle can always be towed with a tow dolly, and any other vehicle can be towed with a trailer if it fits. So I suspect you're looking for a 4-down towable?
If you have your eye on a certain brand/model, you can google it, or find the users guide online and that should tell you how it can be towed. Never go by what a car salesman says though.