I'm 18 and my boyfriend wants me to get an apartment with him and his friend. is this a bad idea?

My boyfriend(He is 18 too) really wants me to move out of my house with my mom and sister and get an apartment with him and his friend. They both work full time and make pretty good money. I want to do this but am afraid of my moms reaction. I just graduated from high school, and I am currently taking night classes to become a CNA. I am planning on working as a CNA and after a year as an LPN. I live with my mom who is overprotective sometimes, but I still love her. We fight a lot though, but I know that if I decided to move it would break her heart because I would dissapoint her. She wanted me to go to college and get a dorm, because she wanted me to have the 'college experience'. But I know that if I told her that I was moving in with Brett and Cage(My boyfriend and his friend) that she would think it is 'trashy' and that I would end up pregnant with screaming kids everywhere. She is a strong catholic and believes that it is wrong to move in with someone before marraige. But I am very miserable at home, and my mom does keep the house pretty disgusting. My mom and sister are so different than me and want to keep me sheltered in this nasty house forever or they want me to go to college and get a dorm, and I cannot afford a university. I would love to go out and live my life and get a nice place with Brett and his friend that is kept nice. Both brett and Cage are very responsible and clean even though they can be immature sometimes. I just don't want to dissapoint my mom. How should I tell her that I am thinking about this? And if I decide to move in how should I tell her and when should I? Is it wrong to move in with my boyfriend this soon and before marraige?