21 and looking to buy a house together? I feel like I want to say you should wait a while but to each his own.
Oh, I don't know ... I find it a bit refreshing that some people can feel that committed at such a young age. My wife and I bought our first house together before we were married and that was 26 years ago. Without knowing Gallandof personally it's hard to judge whether it's a good plan or not.
According to current statistics the divorce rate for couples in the 20-25 age group is highest at just about under 40%, and statistically speaking all first time marriages have only a 50/50 chance of not ending in divorce. Even so, I say go for it. A lifetime of love is worth the statistical risk.
BTW, in the event of divorce, she gets the house so make sure she likes it