Re: asa school vs buying own 20-30ft and teach self?
I don't own a boat but think about it everyday and can only equate your question with riding a motorcycle. Taking the MC class will certify you, get you a license and even an insurance discount but it in no way prepares you for riding on the street.
In fact, most would tell you if they waited a month or two they would be scared to even get on a bike without additional training and basically starting all over again.
My plan is to buy a boat and sail my butt off and maybe get some training for the 1st few outings...