I Know that this may sound cheesy, But I bought a $400 sears treadmill (pro form)for my girlfriend! ANd It works great for cardio sessions. You may want to check your local newspaper or a magazine called the buy and sell I find that there are a lot of people who want to get rid of ther fitness equipment and they are practically giving it away!! I bought a full blown lifecycle for myself in the buy and sell for $500. I know that this might sound like a lot of money for some people but considering that this model is the one that the use in gyms and the retail price is $3000 I think that I got an excellent deal!!!
Best of luck!!