ROTC and SMP? lots of questions?

I need to know about ROTC. Ive heard the SMP pays for some if not all of your college tuition. I assume that means you; have to sign a contract that will hold you responsible to serve after graduation. I also want to know if you were a part of the SMP would you attend basic training the summer before college starts. I would like to get basic training done before college started to get it out of the way. I am now a senior in high school.