I was going to suggest perusing craigslist for a used Bike Friday tandem, BFs can be a really good deal that way, if checked out properly, sounds like you are looking at used. Main thing I would stay away from is ones with an internal gear hub instead of a triple or wide-double crank. Just understand, BF tandems are not so much "folding" tandems, as "take-apart" tandems, they have no hinge so they actually break into pieces, small enough to transport by checked luggage on airlines.

Regarding transport difficulty, you haven't lived until you've transported a Ryan Duplex (below in yellow), (now Longbikes Gulfstream, below in white) long-wheelbase recumbent tandem with no frame couplers; Long minivan, from the back doors to the front wheel between the two front van seats. The one below has frame couplers, my friend's did not: