Bike rentals anyone ?

I agree with Canhostel on this. The only way it would work for my mind is if you happened to be in an area where there was a huge demand for bikes for some reason - such as near a bike trail or something. The basic problem is that people a very hard on the bikes, and tend to wreck them quite quickly. Therefore you need to invest in good quality expensive bikes, and thus need lots of customers to pay for them You also need someone on-site to do maintenance on the bikes regularly - if you have to pay someone extra to do this it hits your potential profit. If you are going to do it in your spare time it will soon take up a fair bit of time. Not sure what country we're talking about, but you might also have to think of insurance - in most western countries this can be quite expensive.

I also would recommend partnering with an existing bike hirer if possible. They will usually have the expertise and bikes available. The biggest problem from a backpackers perspective is that hiring a bike is too expensive for a lot of people. Unfortunately due to the reasons outlined above, it's an expensive business to run.

I think as long as you have 1) the money to buy good quality bikes 2) the time to put into maintenance and 3) enough customer base to make your investment worthwhile then you could definitely make it work. It sounds like you are in area that would suit bike rental. For us insurance (public liability - i.e. someone falling off and hurting themselves) was the killer. For a small operation it was too expensive. And too risky not to have it. It's the same in a lot of businesses - I know of horse riding operations that have closed just because the insurance became too expensive.