https://vw-handiquilter.storage.goog...ms-Oct2015.pdf
The above link gives the space requirements for the various Handi Quilter machines. I am sure other machines will have similar space requirements. Keep in mind this is just the requirement for the machine. Also larger machines will have a greater depth. I am a larger women and I prefer extra space around my machine.
So generally a room that is 3 feet longer and wider than the table. Width will vary a bit based on whether or not you plan to do Pantos. You need to access the back of the machine for Pantos. If your table has casters, you may be able to get by with less room front to back, but if you are designing from scratch, more is better.
Now if you want to store threads, batting, rulers, stencils, pins, red snappers or other leader grips, you will need space for storage units as well.
Then you need room for your sewing machines, ironing board/table, cutting table. Plus fabric storage, books, magazines, patterns, computer to surf the net etc., comfy chair, coffee maker or kettle for tea.
Important to consider, enough electrical outlets on their own breaker. Lots of good lighting, spot, task, movable etc.
You will want one wall blank for your design wall too.
I have my sewing stuff in three different rooms. Probably 400 square feet all together. My HQ 16 is in one room mostly by itself. Fabric, sewing machines and ironing board in room two. More fabric, books, patterns, comfy seating in room three. One day I will remove the walls between the spaces, but not yet.