It is possible, I have accomplished this by being very diversified!
Also it doesn't happen overnight!
I have had my longarm for 6 years so it is now paid for, as well as my other equipment(machines,cutter etc.)
and you have to build a client base
right now I have a steady flow and can't take on more clients, this is because I want to keep them happy. they know that I will have no more that a month turn around on a top and a 2 month on a commissioned quilt.
I also discovered that to keep my costs down I had to buy wholesale, but the buying minimums are high.
So I started making kits, these I sell at very little over my wholesale cost. I don't make a living with these but they do help get my money back for the overpurchasing to meet my minimums. Some of which are $1000-$2000 per order.
you need to be creative and market yourself and your product!
also keep very good records!