Tripper,
I read your "need to have" as "must have" - thought that it was what you meant. And I do have problems with just that. Ask a 'hardcore BH collector' and you'll get some answers which will cost you several thousand Dollars within seconds, but will only provide you with maybe five BH's for your display!
My suggestion for what you "need to have" is, that you ask yourself, what do you want to achieve. If you only look for a wide spread of different kinds and ages, you should have a nice collection for cheap pretty soon. But if you "need" just that one single model, which was assembled befor breakfast, that monday, and therefore lacks the last spotweld over here etc. etc. - get a second job for the money needed.
On the auction site restict yourself to a certain maximum and don't bid more then that. This way you can't step into a trap and you don't get into my way