Small business ownership: My coffeehouse nightmare. - Slate Magazine
There is a golden rule, long cherished by restaurateurs, for determining whether a business is viable. Rent should take up no more than 25 percent of your revenue, another 25 percent should go toward payroll, and 35 percent should go toward the product. The remaining 15 percent is what you take home. There's an even more elegant version of that rule: Make your rent in four days to be profitable, a week to break even. If you haven't hit the latter mark in a month, close.