Well, I'm not sure how close you are to being engaged, but my general advice to people considering moving in with their significant others is "NO". I can see why it might be a benefit to some financially, but I see it more as a "unofficial marriage". As soon as you move in together, that's basically what your married life is like. Either things will be fine and you stay together forever and get married, or you learn a little too much about your partner too soon, all the romance becomes overshadowed by domestic issues and you fall out of love and break up. Besides, you'll be spending ALL of your free time together whether you want to or not. You might regret giving up your privacy and space, I say you should hold onto that as long as you can because once you're married it only becomes more scarce, and after you have kids then it's really gone!
The way I see it, the only thing that REALLY changes about your relationship after marriage is that you live together, and are now thinking in terms of the pair of you. If you start living that way before your married, then the marriage just becomes a really expensive party. Before the party you're living together and cleaning house and working to pay the bills, after the party you're living together and cleaning house and working to pay the bills. NOTHING CHANGES! Give yourself something to look forward to for after you get married and don't live together before you have to.
Also, in some places cohabitation for a certain amount of time would qualify you as his common-law wife. You might want to look into the laws in your area, because you could wind up married to someone you later discover you don't want to spend the rest of your life with. Then you'll have all the legal issues to deal with. Good luck!