My studio is an old wood lean-to off the back of the garage! It is easy walking distance and DH (bless his heart) gutted it and re-walled, put flooring in, etc. It's only 2 feet wider than my longarm table - it's 16 feet long and 8 feet wide. If I had my wish -- I'd have a larger room!!!! I definately need more walking around space. Part of the studio (another 8 feet length is storage) - I'm hoping next summer we can build a shed for the storage and add more space for me!!! :D BTW -- be sure to put in laminate flooring!! I had carpet in there before and it was a pain!!!! I do quilts for a business. I don't know how any place that you put it would interfer with your taxes, etc. You write off a percentage on tax papers. Talk to an accountant to see what your state allows. In our area, you can have an initial meeting for free!
Here's a pic of the studio ---- I've since added two 5 shelf shelves on the left to store customer quilts.