My guess would be many of them who have tried have "failed" There is a learning curve to about anything. If you can't learn enough fast enough chances are you will fail unless you meet someone who knows way more than you do who you can trust to teach you.
I will point out a new truth though. The thing that is currently working is online opportunities for offline sales. Most of what my company offers are those because they are where the money currently is, and with them all being free to join the "will I see return on my investment" question no longer matters. More internet companies are going to this model and quickly because it is what is currently working.
We are seeing even this as something hard because people no longer believe you can get value for "free" if they ever did. We are making more money from these free opportunities than I do from hub pages. It does take more than one person in my case because I have been wheelchair bound for 20 years.
In my case there was no choice. Quite a few times taking something someone said at face value, which I no longer do, cost over a years income. The money tied up has to be replaced somehow.