First, I wanted to send you to John Scalzi's post, Advice to New Writers About Money. (Thanks, Angie, for the link.) Smart words. And damn, I shoulda married a guy with health insurance. Well, I love DH anyway. What can you do?
I wouldn't exactly call myself an expert on freelancing and money. I would say that I've learned a whole lot the hard way, LOL.
First up, the spouse with health insurance is probably the number one thing I wish I had, at the moment. No, no, no, I don't want to trade in my spouse, and I don't want him to change his lifestyle. Just sayin'. Health insurance and dental insurance would be awesome.
The second thing I've learned the hard way, this year in fact, is that there are only two directions for a business: growing or shrinking. Maintaining the optimal work/life balance is near impossible, because you must account for people not paying, for people paying you way late, for expected incomes to fall through.
So I'm learning I always need to take more work than the budget needs, in order to account for the above.
Just because you're turning away work by the droves one month, doesn't mean that six months later they'll still be calling. Six months later, you might discover you want/need more, and no one's calling.
To a certain extant, take all the work you can, when you can get it. If there's a balance, I haven't found it.
Third, do not have a person with a business degree manage the finances. I learned this one the hard way, too. They think too theoretically. They think, "we're supposed to get X amount this month, and pay out Y amount this month." Problem is, cash flow never works that way.
You just can't count on the money coming when it's expected to come.
And finally, as a writer, you're probably a creative person. Applying that creativity and imagination to finding ways to make money "outside the box" will help tremendously.
That's one of the things I've always loved most about working for myself. Unlike punching a clock and putting in time, working for myself means I'm making money. I'm not limited by a salary. I can always find new ways to bring in more income.
Speaking of bringing in more income, I've got a story to write and a root canal to pay for ...