First, welcome aboard. You will find lots on knowledgable folks here.
Some cars/trucks are towable and some are not by the design of the transmission. Best place to find out if either of your vehicles are towable and what modifications need to be made is at REMCO Towing.
With your class A you also need to be aware of the towing limits of the chassis and the hitch rating. A lot of RV's have 3500# rated hitches which will rule out the Crown Vic.
Your chassis may also have a 1000# or 1500# limit on towing a load without auxillary brakes on the towed load.
So with modifications,tow bar and brakes you are probably looking at $2500.00 and up to roll with a dinghy attached.
Have fun shoping.