I came across this thread on CF and thought it might help in your planning.
Cruising on $500 per Month . . . - Cruisers & Sailing Forums
Lots of good discussion on what items need to be in your budget, what is critical spending and what kind of life you'll lead at $500/mo budget. There are, of course, differing opinions throughout the thread on what is necessary, what is missing etc. So lots to help you create your own particular financial plan while you save up at your current job.