Living Together...the Same As Marriage?

Well I have seen alot of the "How young is too young?" posts. I`ve seen that some ppl respond by saying "don`t get married. You`re too young. Why dont you just try living together...things change once you get the ring on your finger".
Im 17 turning 18 in April. I have been with my boyfriend for almost a year. We`ve talked about everthing that other ppl suggest talking about pre-marriage....money/budgeting, education, children..raising them(how many, religion,etc)...even what we thought about adoption.
We talk about moving in together. At first, he was the one that started with the comments about living together and I wasn`t really thinking that way at the time. Now it seems like Im the one always bringing it up... He tells me that he`s scared and everytime we talk about it he compares us to his friends that are living with thier girlfriends. One of his friends and his gf just broke up but what does he expect? they dated for about a month before moving in together! Everything that goes wrong with them makes him more scared...he thinks that`s going to be us. I try to explain to him that we are not the same...how could he compare us to them? He is also scared that we are going to change for the worse...that we are going to stop saying cute things to each other...that the stuff he likes about our relationship now is going to stop once we move in together. He also worries about not being able to care of me financially...he wants to give me whatever I want...he doesn`t want to deny me anything.
I understand all of his concerns, but some of them like comparing us to his friends, are just ridiculous because we are nothing alike. And I think that these concerns you never really get over... Because if you`re scared things are going to change, you`re still going to be scared 5 months from now.
Tell me what you think about my situation. And also tell me you`re views about living together...is it the same as marriage or completely different?