It's a rough business, but many of us here are making a full time living. Like any other business, if you want to be profitable, you must know your market, offer something they want, and have a good plan. It's even more important in a competitive, unpredictable, small margin business like a studio.
Part of the planning includes access to start up capital since you need to invest quite a bit before even opening the door, and have enough to weather the first couple of years in a business that is fairly slow to ramp up and recoup. The other thing is to have some business already lined up before opening the door. Offer additional services that can feed each other. If you add post services, offer composition as well. Or try to bring in some independenet video editors if you have some extra space. That can get you audio post work from their video clients.
One challenge is imposed because many people enter the studio business with no plan to be profitable. Three possible scenarios include somebody with family money who starts a studio for the glamour and not needing to make the monthly nut to continue; a successful musician who again doesnt need to make the business numbers work to remain afloat; or somebody who just has no business plan or skills and hopes that if they build it... These three versions of studio businesses unfortunately are not concerned with numbers that work, so they spend more than they make and charge less than they need to stay in the black, and that makes legitimate businesspeople unable to compete in many cases. It drags down the whole profession and makes studios either wealthy play toys or unprofessional wanna-bes.
Even with the risky, oversaturated nature of the business, there are several examples of people that get it right and make a profit. As older studios fail, newer ones are coming online, some with creative businesspeople at the helm figuring new ways to be sucessful in the changing market. If you manage to get a reasonable idea of how it's changing and where it may be going, especially in your specific market, and have the capital to take advantage of it, then you have a reasonable chance of at least modest profitability. There's always the "lottery ticket" approach and you may get lucky, but don't count on it. Make real world decisions and never forget it's a business. You are unlikely to get rich, but you can make a living doing what you love.