Date, marriage, move in?

So my boyfriend (26) and I (22) have been dating for a little over 1 &1/2 and we both know we are it for each other. We have been looking for a place to move into together and when I brought it up to my parents my mom freaked and said "marriage then you move out". I know my mom was a teen mom and she was married young (before my dad) and she realized that is as a huge mistake. But we are in a different time. I see her point and she's also very traditional, but I'm going to be 23 we live in a 2 bedroom apt, along with my 18 year old brother, I need my own space. Any advice on how to try and have them see my side.