I second (or third) the suggestion of the Leslie Sanson "Walk Away the Pounds" DVDs, especially if you are just getting started. They are easy to follow, don't require much of any equipment or space, and are not terribly challenging.
I have a couple that I do as a back up to my other more strenous workouts. I use ankle weights and wrist weights to make the workout more intense. The walks themselves sometimes call for her "Walk Away Weighted Balls" but you could use regular handweights or even soup cans! Other than that you only need sneakers (although I almost always do it barefoot on my carpet at home). If I were you, I would definitely challenge myself to commit to following an exercise program for several months before I would invest any money in a large piece of equipment. I had been following my walking program faithfully for four months before I broke down and invested in my treadmill. That was about 9 years ago. I have gone through spurts of it being used as a clothing hanger, but for the most part it sees pretty regular use.
I also have a "Cardioglide" (popular tv informercial equipment from about 10 years ago) that I got for free at a yard sale. It gets used in spurts, but it is easy to put away in the basement when I don't want it hanging around. And I got a mini-trampoline for free at our town dump. It was actually in better shape than the one I paid $7 for at a yard sale! So you can find decent stuff out there for cheap/free.
Good luck, no matter what you decide......................P