Yes, what you are about to do requires focus, dedication, and a bit of insanity. I am finally a senior at the University of North Texas and began my freshman year working 50hrs a week and taking 12 hours of school. I have been working and going to school full time for 4 years now, and I have a 3.0 GPA. After a few semesters, you really end up figuring out what works for you, usually at the expense of your GPA or sub-par work performance. Right now, my "ideal" work/school balance is as follows: Working 4 days one week, 5 days the next; this includes working every Saturday. For school, I am taking 15 hours this semester and need 15 more in the spring to graduate. So I average around 35 hours per week and take 15 hours of upper level business classes. Nice, huh?
Here is the kicker - you will eventually go INSANE! I am a very laid-back person, but I have had a tremendous time dealing with the stress that comes from everything. I work at a retail corporation in a middle management role. The paychecks and experience are great, the stress is horrible. I would recommend getting a job that does not require too much critical thinking and that does not carry enormous expectations. It is very hard not to take home work issues with you. My job expectations are difficult to fulfill working 40+ hours per week, let alone 35.
With school, you have to make it the #1 priority over everything else. If you cannot do that or are not yet willing to do that, you are wasting your time. Save your money and wait til you are ready to commit. I have had to drop many classes and have had to do a few over as well because of the enormous weight of it all (There were also two semesters when I had to drop classes due to a torn ACL and a death in the family). Your major and your GPA will make or break the beginning of your professional life, seriously. Your GPA is your baby.
Essentially, you cannot afford to have much of a social life, if any. I rarely see my family and friends. I basically spend time with my girlfriend (which I also do not recommend if you are working and going to school full-time unless you both are seriously involved) and go out once or twice as week, usually at the expense of sleep. I end up having a few hours a week to do some fun things, but I end up feeling guilty about it because I could be using that time to study! I have not been on a vacation since I started school. There literally is no time.
I would say that working and going to school full time has its benefits. You get valuable experience and a paycheck to take care of financial obligations. You are also able to apply your education to your current job responsibilities. Some companies even pay some of your tuition bill! The negatives include constant stress, depression, poorer health, loss of social life and weakened relationships, less opportunity to enjoy the best years of your life. Is it worth it? I would say NO. I only work because I have refused to take out monster private loans in order to pay for living expenses. As I am in midst of my senior year, the stress is really getting to me and I may die soon. I am considering taking out a small private loan and working part-time at 20 hours a week. 15 hours a week plus reduced stress sounds great right about... NOW! :)