I first saw these being rented in Homer, Alaska. Thought they were cool and did a little home work. Near where I live there's 125 miles of bike trail that's improved, 6 feet wide, and near level. I would have considered rentals, tours, and senior citizen socials with picnic, but didn't want to obligate every summer weekend.

They're also refered to as a Quadracycle, Surrey and a 2 or 4 person bike. They range from about $600 to $3000 for the motor assisted ones. I've seen 3 used ones on ebay in the past year.

There's lots of info to be found using various search engines. Here's a list of worldwide manufactures. Workbike.org click on "makers".

Here's some rental info. Home.aspx - Wheel Fun Rentals

Some bicycle shops rent them. Be sure to try before you buy.