Your scenario meets the definition of 'using margin as a financing option'. It is the same as the overdraft option provided by credit cards, only it is more dangerous since in the margin call scenario they actually liquidate your stocks without asking you (if I recall from reading up on how this works at most discount brokerages a few years ago). The fact that you rarely do it helps some but as we know the thing about rare events is they happen every day :). I have held myself to a "current ratio" of over two, which is considered 'healthy' by most finance people when evaluating businesses. I would encourage everyone to calculate their current ratio and make sure it is ALWAYS over two as well. It's literally the current assets (cash you could get access to in a year) divided by the current liabilities (all expenses due in a year). Easy to calculate and immensely freeing once you decide it's a rule you'll never break.