Getting married young???

Sa
So my boyfriend told me I'm the LOVE of his life and he wants to get married and have kids with me. I completly feel the same way for him. BUT he graduated high school last year and I'm almost done. 
He wants me to move in with with after I graduate. He wants to get married and start our life together ASAP . thing is, I'm not sure what being married at 18 will be like. Any advice? Is this crazy?