Flush draw: calling a flop bet, or raising for free card??

[Beck]

The following situation is fictional, but one I encounter often:

I limp with a suited ace, and when the flop comes, I got 2 people to act before and 2 to act behind me.
I assume that if I make the Nut flush I win the hand (which isn't always so, I know)

The flop gives me a nut flush draw, but no pair.
Early position bets out, 1 folds, hero??

If I call, and the 2 behind me folds, well, I had the odds to call the bet.
If I call, and 2 behind me also calls, I basically made money, since I flush 35% if going all the way, and with 3 people besides me putting a bet in at flop, I would only need 25% win, right?

Or put in another way: For every bet I put in at the flop, as long as 2 other come along, that's a break even play, right?

So what if I try to raise to get a free card?
If they both fold behind me, the early bettor calls, and I get the free card, well that's fine.
If I get 1 behind me and the original bettor to call, then yt's break even.
If they both call behind me, well, then I just pumped my flush draw.

What I'm getting at, when I'm out of position, when should I just call with my flush draw, and when should I raise?

I know, that if the 2 behind me folds, and early bettor 3-bets, then it's a bad play, but isn't that made up for, with the times, Iget free cards, pump my draw, perhaps make a semibluff on the turn taking the pot etc.??

If my scenario is unclear, please let me know, and I'll try to explain my thoughts further.