Is he too old?

My stepmom introduced me to one of her regulars at work, because she thought we would like each other and she was also shit faced. Well, we did end up liking each other that night. The next day I asked for her to help me out with him and she said no. At this point she's sober and saying that he's way too old for me, for I'm 17 and a senior and he just turned 21. Everyone I know says that that would be okay if we dated. My stepmom said we could be friends, but until I'm either 18 or out of high school, it's creepy for us to date. However, she said that we could be friends and after awhile if we still liked each other, we could date while I'm finishing up my senior year. I've never had a boyfriend before, so I don't know what's wrong and right. Any help will be awesome. Thank you.