Mike,
I made my first gazillion (
) renting bikes and surreys at the jersey shore.
I had about 12 surreys at $5k each and they would last for about 3 years and I'd rent them for $15.00/hr.
As soon as I saw the Segway I thought to myself "I need to get back into the rental business..."
The thoughts I'd have with it are how long is the learning curve before you can set a renter loose and insurance cost/availability.