Buy low, sell high. Never take a loss. Always grab a bargain.
And Rule #1.....
Don't pay more than you reasonably expect the value will be in your lifetime.
(In other words, $1200 for a run-of-the-mill Model 60, like I saw not too long ago on a certain classified page someplace, is ridiculous. And this is after I paid $399 for one in the last year. You can do much better.)