It depends on what you're going to college for. If it's for a general education, like a Bachelor's Degree, then it's practically worthless in today's specialized market. If you want something more specialized like law, business, or medicine then a college degree is mandatory. Crunch numbers on tuition costs, etc., and weigh that with job prospects for your field.
A career online could be anything. Much depends on your personality. If you're a self-starter with lots of drive and ambition then you might make it. But that's what it takes. It's like home schooling except you are the student AND the teacher.
If by "career online" you're referring to getting a degree via long-distance learning options you probably won't save any money. Regardless, find something you like, learn all you can about it, and -- most importantly -- stick with it. Giving up when the going gets tough is pointless.