Inexpensive is one of the BIG reasons my entire family loves geocaching. We find several caches close by so we can do them all in a short driving distance. I've got a bag specifically for geocaching....swag items, sunscreen, bug spray, bandaids, extra pens and small notebook incase the cache we find needs a new one and most importantly an extra set of batteries for the GPS. I usually pack a lunch/snacks and drinks.
We're so busy on our treasure hunts it doesn't seem like "exercise" and we've discovered so great areas close to home we never knew about.
Start saving your swag ( swap ) items now. I pick up inexpensive keychains, toys, pins etc on sale and clearance. My local Post Office recently had a clearance bin full of hat pins, fridge magnets and keychains for 50 cents each. You know the ones they sell that are usually $5 each. I bought every one they had. Then had the fun of explaining to the PO lady about geocaching.