Grad school or work?

[TMDG]

I'm graduating with a BS in engineering in about 2 weeks and I've secured a full time position as a financial analyst. I know I want to go into finance, but the kind of work I want to do does not really align with the job offer I have now. Basically, I want to work as a quantitative trader or researcher eventually applying some pretty advanced math to the financial markets, building and implementing all sorts of models. This would most likely require an advanced degree and, because of that, I have also applied to several quantitative finance master's programs. I won't hear from these schools until around March. So, now I have to decide between accepting this full time position or rejecting it and waiting to see whether or not I get into school. I've only applied to the top 5 schools because from what I've heard, the name of the university is very important in getting jobs in this industry and the lower tier schools aren't really worth the money (around 40k for a year and a half which is pretty significant for me). These programs are pretty competitive, and even though I have pretty good grades, I think my chances of getting accepted into at least one program are only around 50%. If I take that route and don't get into any schools, I plan on looking for jobs in the springtime, working for a few years while taking some night classes to strengthen my profile, and apply again in a few years.

What would you guys suggest I do? I assume it would be pretty bad to take the full time position and leave the company next Sept if I happen to get into a school?

FWIW, the full-time position I got kinda fell into my lap because an older friend set up an interview for me and encouraged me to try to get the job. He obviously thinks it'll be best to get some work experience before going back to school. One of the reasons I'm leaning towards going to school first instead of working for a few years is that I've heard it's pretty hard to go from working and making money to doing problem sets and studying for exams without getting paid. Anyone have experience with this?