Say you’re a dentist. You’ve built up a strong practice over 25 years, and now you want to sell. You’ve been socking away cash into the stock market so you’ve seen for yourself how much steady, profitable businesses are worth. Stock market investors pay 15 to 25 times operating profits for public companies not unlike your little dental practice. And everyone is agreed that the market for private companies is hot.  You do the sums in your head and calculate that at a sale price of 15 times operating profits (being conservative) you will be able to afford either a…