Gender-Swapped by a Billionaire

Greg and Loren have just moved to a city, but they've gotten some strange mail. It's an offer from a wealthy man who wants them to be part of a magical experiment. He claims he can have a spell cast on them both that changes their genders.

They think it can't possibly be real, but with a nice compensation offer on the table, they decide they want to see for themselves. And besides, if it really does work...

How much fun would that be?