Google Adsense? I need some help!?

I would like to start a business with Google Adsense as the basis. You try and separate the fluff from the fact but you get swamped and overrun with info that you don't know if it is factual or not. I want to know the answer to these questions: Can you start with Google Adsense on your own or do you have to join someone else's site to get it? Is there No Cost or a One Time Fee or is there Ongoing Investments you have to make? Is there one site better then another to give me straightforward, honest advice about staying on course with this or am I doomed to hearing from everyone that their course/advice/blog site is the best thing since sliced bread? Any other honest, well-meant advice you can give me to swim thru the quagmire of BS that is out there would be greatly appreciated.