Dave Klecha at Featherish talks about working out on a budget:

There’s a couple of common issues that most beginners in exercise face. One is the expense. As I mentioned before, my future sister-in-law recently dropped $1800 on a bike, which she only uses to train for and race in triathalons. Gym memberships can cost anywhere from $50 and up per month, and most of the equipment you can buy for use at home is also a significant expense. And, for instance, if you find your body can’t handle weight training, or your schedule doesn’t allow for an hour of road biking per day, you might dump a lot of money into something that will only get used a couple times then, if you’re lucky, sold on E-bay for half what you paid for it.