Just plan on it being the size of your living room. and large enough to accomidate 3+ machines and a long arm set up. with one wall dedicated to fabric and a roll or two of batting. this wall can be set up with your long arm on it. then the other wall is your design wall on the opposite side. your machines will be three feet out from this wall so that while you are sewing you can look at it every now and then. the third wall will be where cutting and ironing will take place. this would be a shorter wall, if you want. I would make sure that the design wall and the short wall has windows. I would also make sure that there is an outlet every 2-3 feet. and lots of pot lights and eyeballs that can be turned in different directions to help illuminate what you need it too. a good 9-10 foot ceiling is also very helpful. just my two cents.