Adsense site, making min.10usd a day.

Hello I´m new to web devlopment and have read alot about adsenses. people claim to make 200-300USD a day, well im not stupid, but you would probably be able to earn a few buck evry day. I have never done anything like this before so I would need a complete walktrough. I dont know what budget i should use, and honestly i dont see why people are making sites other will earn from, when they could just do it themself and earn themself. Well, if you are intrestesd I would like to see a plan for the project before you go ahead.