Another way to make money without any expense is with the Pay to Click programmes. When you sign up with one of these programmes, you are given some sites to click on for 30 seconds and you are paid - usually $0.01 per click. Now this is going to make me a fortune, even clicking every day, but you can generate referrals and get percentages from their clicks.
I have read that a lot of these programmes are not so reputable and that people have had problems in getting paid, but there is one that generally seems to get good reviews - ClickSense. I've signed up for it and set aside some time every day for "casual clicking". You can sign up easily here -