I just purchased a used 2013 Ford Fiesta automatic tranny to be used the same as you, only for towing on trips, for a lot less than 15k. Other than setting the tranny in Neutral, the only thing to do is disconnect the negative post on the battery. The Fiesta negative battery post is easily accessible (where the Focus is not) so it takes 30 seconds with a 10mm nut driver to disconnect the battery. There are no mileage limits on towing it, and max speed for towing is 70 mph. The Fiesta weighs only 2,600 lbs, so I doubt I will even now it's there. I'm still getting estimates on the tow setup, so I haven't towed yet, but from what I've read on this forum, folks love the little Fiesta.
Good luck with your search, and safe travels.