Psychology - Confused in Relationship???????

I've been with my boyfriend for 2 years and we started to live together in December 2007. He owns an appartment and so do I, but eventually, I'd like us both to sell up and buy a nice house together that we own jointly. My boyfriend says he feels ready to marry me but not to buy a house with me..I don't understand why? If he is willing to commit to me in marriage why won't he commit to me financially but us both buying a house together. (We earn the same money and have similar amounts of equity)..