Originally Posted by QuiltE
Being that the custom sewing is your job/business, then it's also part of that business for you to finish the room that was intended for it. Just.Do.It!
Yes, there is another problem ... it has been used for sometime for other than for your business. And it appears that it's been for more than storage ... you mentioned a flat screen, and his watching TV. Looks like he has changed this into his man-cave.
Take hold ... and start emptying the stuff, and converting it back to your Business Location!
Hon, you have to take charge. If it was originally intended for your business you need to claim your space. It doesn't have to have drywall to make it a studio. I ran a custom window treatment business in South Carolina for 10 years with just studwork and concrete floor. It was a lucretive business despite the fact I had a view of black tarp on the ceiling and insulation batting on the walls between the studs. It still suffices. Besides it's easier to find studs to hang shelving.... lol Just a note, after I divorced in 2000 and moved back to TN, a couple of years later he finally finished out the downstairs... go figure. Now I have a Victorian with lots of space to roam, and can put my shop any place I please. Sometimes karma is nice. Good luck to you in your business and decisions.