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If you have a car and live near a popular hiking/cycling trail, you can make a small fortune by transporting people's backpacks and stuff from one campsite/youth hostel etc, to another, thereby enabling them to walk freely and without encumbering luggage.

I worked with a guy who did this on the Hadrian's Wall UNESCO World Heritage walking trail, and during the peak season he could make over $200 a day.

Similarly, if you have a shed, barn or outhouse, opening it as a camping barn (just floorspace but under a roof and therefore sheltered from elements, but people have to bring their own sleeping gear) you can have a steady income that peaks hugely in the summer. If you have a field or any amount of open space, installing a toilet cubicle and water supply is a pretty low investment way of making it work for you as a campsite.

when I think of ways to make money I tend to always think of how to get the maximum mileage out of assets I already have, and whether some things I have actually are assets or could be, that I didn't previously think of as such.