Rebuys require a larger bankroll and a different approach (in the rebuy period).
To profit from Rebuys, you have to have the right attitude. Assume that the cost to you is going to be at least 3 buyins. For example, a $10 +$1 Rebuy is really a $31 MTT. If that worries you, find a cheaper game.
In the Rebuy period, it is highly likely that some (at least) of your opponents will play very loose and very aggressively. If you don`t feel comfortable in that environment, again, don`t enter.
However, as Sindri says, assuming you have the measure of them, a Rebuy offers the opportunity to play deep-stack after the rebuy period ends. This is +EV if you are a strong MTT player.