[Cooker]

When using effective odds, you are basically thinking about going all the way to the river, so you must include the current and all future bets on both sides of the pot odds (you can even include some implied odds if you hit). In the case of a 4 flush, this means you only need 2 to 1 on the current plus all future bets in order to go to the river.

For your specific example, this works out as:

effective pot = $10 + $2 (other callers this round) + $4 (other callers on the turn) = $16

your effective bet = $1 (bet this round) + $2 (bet on turn) = $3

So your effective pot odds are 16 to 3 or 5.3 to 1, so you should definitely plan to call all the way to the river. For implied odds, you could also include the bet on the river if you hit into the effective pot, but you don't need to include your bet on the river into your effective bet, because you won't even call a bet on the end if you don't hit. In general, I would be more conservative with assuming the number of other players that will stay in to the river, but you specifically stated that all 3 would stay in. It is pretty well known that if 2 opponents will stay to the river with you, you are always correct to call all bets with a flush draw, since you will automatically be getting 2 to 1 on all current and future bets.

If your effective odds don't indicate a call, you may still be correct to take 1 more card, but then you must have a full 4 to 1 in pot odds not considering future bets.

If you have position and think a raise will buy you a free card on the turn, you only need to be getting 2 to 1 on a raise with the current pot, because you won't have to pay any extra bets to see the river. For this play, you must know your opponents are capable of slowing down enough, because getting reraised on the flop and bet into on the turn if you don't hit would be a disaster (and you must do this to tricky devils that try this play against you).

There are many considerations to playing these strong draws, but in low limit, you will often have enough callers post flop to allow a lot of flexibility in your play and still be getting correct odds. I think saying you must have 4 to 1 is really costing one a lot of profitable situations in low limit games.

In no limit you must almost always have 4 to 1 except in cases where you or your opponent is all in, in which case you only need 2 to 1 since there will be no future bets. This is because there is no way to accurately estimate the bet you will be facing on the turn if you miss in NL.