Learning how to earn money without investment in the online world is a tough thing to do. I know, I've been at it for 3 years and real help and advice is hard to come by. I only really began to find any real success over the last 6-8 months and guess what; it does take a little investment. But beware! The majority of sites that you will visit that claim to help you do these are usually trying to sell you something or get you on their mailing list so they can sell to you at a later date.
There is nothing wrong with this to my mind however, as long as they are pointing you towards products that will actually help you. All too often however they will sell you a product that is sub standard or only really benefits them in some way, usually financially.
I remember about 2 years ago I bought a 'turnkey' website, they claimed that I would get a blog, they would provide all the content and help me to sell thousands of dollars worth of ClickBank products. I excitedly logged into my new WordPress site that they had created for me, only to find that I could not change a bloody thing to the way I wanted it. They had links back to their main site on every page to help their rankings and the support was pretty much useless.
On top of this, I had no clue how to rank a site in Google below on page optimization and maybe doing some blog commentary. As you may have guessed, they did not tell you how to rank well either, even though they obviously knew how to rank well themselves.
I asked for my money back of course, and got most of it. (Apart from about $ 30 that I was stupid enough to part with on a useless up sell from one of their JV partners) A small loss financially but but I look at it as a lesson that I paid for. I'm just happy that I knew enough about WordPress at that time to see I was getting swindled. There are probably hundreds of who were not lucky enough to be armed with that info however and probably spent months trying to work out why they were not selling anything.
The point is this: Many will claim to be able to teach you how to earn money without investment, just to get your email address from you so that they can keep recommending products which you have to buy.
Your best bet is to find a source of honest information where you are not sold at every 5 minutes by an email auto responder.