You know me. I think the amount of space that lawyers need to do their work is exaggerated. It is more ego than necessity, and it leads to a cluttered and complicated life. But, a quiet dedicated work space is good. If you do not have room in your home, then try building a space in back or close to your home. It might be a little industrial shabby chic, but throw in some windows and some planting and you are good to go.
In Berkeley, California Karl Wanaselja, along with his business partner and wife Cate Leger, created their home-office using an old refrigerated shipping container that cost just $1,800. They cut their 40' long refrigerated unit in half and placed it in a T shape in their backyard. Because it was a refrigerated container, they did not need to add any insulation. Using a reciprocating saw, the couple cut huge windows into the aluminum/stainless steel structure.
You can see for yourself.