I did this. Started literally from the bottom. Didn't invest any money in the first 6 months (I simply didn't have money to invest in the very beginning).
2013 I started creating blogs (Blogposts, wordpress etc. - for free) in different niches, ranked them on Google (with web 2.0 and other free links) and earned money via CPA networks. Made me a few hundred bucks until I bought my own hosting and domains to get a higher conversation rate etc.
It is absolutely possible to earn without investing, you just need more discipline and work harder.
And don't let anyone tell you IT IS NOT possible. It is possible. Think out of the box
Little motivation: Since then I made $xxx,xxx, travelled to any country I want, lived in some nice places, bought my own apartment and a nice car. Started from the bottom now we here