Rear coaster brake would help the braking somewhat but still...Looks early 1970s when that folder style was in vogue.
With steel rims that thing would be a deathtrap for braking in the wet. I suppose it would be OK as a beach cruiser for a few km, otherwise I would think riding it would be a misery. Braking and a stiff frame for decent handling make or break the pleasure of tandeming. That one looks wibbly and scary.