Wow, WayneDave is right, there are options galore! Not to plug, but if you visit me you will see quite a few hubs on this subject. If money is an issue than definitely get a jump rope, a heavy bag if you have a place for it, or even a speed bag set up. There is some stress relief for you right there! I have plenty of room for 'stuff' in my garage and outside, but I do a lot of bodyweight (and tae kwon do) at home. I learned a lot of it from bodyweightcoach.com, they have some great ideas. Look up Scott Sonnon as well. Also, pick up a cheap pair of adjustable dumbbells. There are endless dumbbell complexes (intervals) you can do and they don't take up much space. Anyhow, I could go on and on, but I've written a lot about this, so if you have the time check out my hubs and my mosladder blog. Have fun!