I also can't afford to get a membership anywhere with a rock wall... or anywhere in general really... to do any of the activities I find less loathsome, so what kind of adventuring can you do on some pennies and a piece of lent??
I'm a teacher, a writer, an artist--mostly sedentary 24/7--but I love exploring and spent a year wandering around in Russia while teaching English. (By the way, teaching has got to be the worst job for your health. I work 12 or more hours a day between planning, teaching, and grading. Parents are always on my case, and the kids are all years behind. And on good days, people bring mountains of doughnuts into the lounge!)
I've never worried about my health because I'm scrawny, but my heart has been dodgy from the stress and total lack of physical activity. I have an exercise bike, but I hate using it. I am much more likely to do the laundry or brush up on me pre-cal than touch it even for half an hour! Working out the traditional way just bores me to tears!