All good points guys!
Not sure how much the hitches would cost...maybe around $75 - $125 depending on the bike. For example, the metropolitan and Vespa hitches were relatively simple. The Honda Ruckus hitch was very elaborate and complicated...so I guess it would depend on the bike.
Me: Hey biker / welder dude, can you help me make a cart for my scooter? I'm gonna ride 10,000 mi across 3 countries on my 50cc scooter for charity.
Dude: Are you for real? You call me. You've got a lot of explaining to do to convince me that you are a NUT on a 50cc mission from God.