Married at 18?

Me and my boyfriend have been together for a year and a half I love him with all my heart and we’re both financially stable. We both have our own full time jobs and we’re wanting to move in together. The problem is my parents said if I want to live with him I have to get married. I love him but we don’t have enough money for the wedding I want and we won’t be able to invite many people. The problem is you only get married once (for most) and I want to make it special. I’ve tried telling my parents that we want to still be able to live together but wait on marriage just so we can make it special and actually have a ceremony. When I told them this they said they wouldn’t help with the wedding, they would cut me off financially and they wouldn’t pay for my college. Does anyone have advice?