Yeah, you have to decide in general what kind a vehicle you want and then do some research to find something of that type that can be towed four down. Some like my Jeep you put the transfer case in neutral and tow it with the tranny in park and the key out. Others you may be able to tow in neutral with the key on. These will likely need to be wired to charge the battery from the MH unless you disconnect the battery while towing.
Others may need to have a lube pump installed on the tranny to keep it lubricated. My previous toad was a '99 Buick Regal and it fell into this category - key on, in neutral, charging line from the rig and the Remco lube pump.
Still others can only be towed with a drive shaft disconnect. Then finally there are ones that cannot be towed at all - alot of all-wheel drives are in this category.
Then there's the whole dolly route. Even there, some vehicles can't be towed that way either - again probably AWD in alot of cases.