Originally Posted by kcanuck
Anything better than 2 : 1
Only if you are all in. This is SUCH a common mistake: 2:1 is the odds if you get to see both
cards. Clearly if there will be a bet on the turn, you can't use the odds for two cards to come to calculate your draw. You really need to calculate your odds one street at a time
. As such, you are a little more than a 4:1 dog.
The real answer to this has to take into account some other factors, including if you might get a free card on the turn if you call, and most importantly, implied odds: how much you can expect to make from your opponent if you hit your flush, which might be 'zero' since the flush will usually be pretty easy to see. Obvioulsy the deeper the stacks, and poorer your opponent, the better. Sammy Farha once said "Why draw if you're not going to get paid off?"
You can see how being in position is a huge advantage here when on the draw, and gives you more options.
Sorry, another "it depends" answer, but hey, it's poker, what did you expect.