My studio is in my house, and I love it this way.
Some of the major benefits:
Renting or buying an outside office is expensive to own, insure, heat, cool and maintain.
Not having an outside space = lower overhead = money saved that I pass along to my clients.
I work late hours. It’s nice not having to drive home from a dark office building at 2 or 3 am.
I am more productive because I spend less time driving to and from work.
Less driving = better for the environment.
But there is one major downside to the home office:
You've got to keep your entire house clean because clients want to see it!