For four down is easiest if what ever you have in the driveway already can roll on all four wheels. If not a dolly works well for most front wheel drive vehicles. A trailer is probably the most difficult and expensive but anything that can get up the ramps could be taken along. Advantages and disadvantages with each set up.
If you have a vehicle that will roll four down then go that route. If not dolly rather than going out and buying a car that can, for now. Used dollies pop up on Craig's List and such and could cost less than a tow bar and base plate. An open or even enclosed vehicle trailer with a vehicle on it is going to be very heavy and expensive. Probably heavier then a gas and some diesel coaches can safety tow but it you have something special an enclosed trailer might be your only choice.