I've known many people who've made a living well into their 50's doing freelance work, and they lived quite comfortably (nice car, nice house, nice and long vacations, etc.). Not web design, but I can't imagine IT and database apps are dramatically different from design for freelancers. I did freelance work on and off for about five or six years, and was always well-paid when I did.

Treat your customers better than they deserve, work dramatically harder than you would if you were on the payroll, charge through the nose, and make sure you interact more with the customer than the design (or servers, or database, or whatever; the way you explain things is more important than what you do...you have to do a good job, but if you fail to explain it well and in a way the client understands, you won't get referrals and you won't make the client happy). These are the keys to living happily and being well-paid in a freelance business.