First, is your Fiesta flat towable? You must confirm this before you go any further. Only certain cars and certain model years are flat towable. Or perhaps it's a manual transmission and not an automatic.
Give us the details - model year, and exact model like Fiesta STS, or whatever it is.
That will give us enough info to determine if it's flat-towable.
Then you'll need a specific BASEPLATE. And that must be installed. That usually costs about $600 for the baseplate and $500 for installation unless you can install it yourself.
Then you'll need a Towbar - those cost beteen $800 and $1,200 depending on which one you buy.
Finally, you'll need an Auxillary Braking System this will cost between $1000 to $2000 depending on what you purchase.
You can buy a used towbar and a used portable Aux Braking System but you'll likely still pay $1000 or more for those two items combine USED. And, you'll still need a Baseplate installed. And those are seldom if ever available used as each on is unique to the car you want to tow.
Lastly, you'll need lights for brake lights and turn signals on the Fiesta. These can be magnetic and only $150 or so.
Getting your Fiesta - if it's eligible to be flat towed - outfitted to tow will cost you $3000 to $4000.
Buying a used Tow Dolly will be much less expensive, just more hassle. And, pretty much any front wheel drive vehicle can be put on a tow dolly. You'll likely find a used tow dolly between $600 and $1,000. You can rent a tow dolly from U-Haul, but it may cost as much to rent as it is to buy a used one that's you'd own.
You might find it much cheaper to drive the Fiesta behind the RV if you don't plan on towing the car for a number of trips.
