Marilyn, I have a large bedroom that I turned into my sewing room. It's not as large as our room but it's large enough for two people if it was for the intended use. I have 2 machines set up, one is a large table and the other is a sewing machine cabinet type for my Bernina.
I also have a double closet. My husband made shelves for me and it's great- holds a ton.
I don't have a longarm so I don't know how much space you need but I'm sure you do.
How exciting! Be sure to post pics.