I have a retired friend who supplements her retirement income with quilting for others. She's been at it 10 years, is finally starting to get some traction and returning customers, and now has to move to be closer to her kids and adult grandkids. There were months when she'd quilt 3-4 quilts, and months where she'd have no business at all. She did a ton of charity quilting for her local guild before finally starting to get some customers. She has robotics and charged $.014 per square inch. She lives in a tiny town in a remote area of the state where there's not a lot of industry or commerce, so her pricing has to be lower. If she was in a major metropolitan area such as Portland, she could charge more ($.20/sq in) but of course she'd also have a lot more competition.
Another thing to consider is dealing with customers. For the most part, quilters are wonderful, but you still get the ones who will bring you quilts with horribly wonky seams and ruffly borders, then complain and refuse to pay when you can't "quilt that out".