In this case the men had to become established, come up with an idea, scout out a suitable target, and then seek financing AND authority from figures higher up in the organization. They have to have the plan reviewed and costs estimated and suitable targets to get the money. This is a common characteristic of al-Qeada operations.
In Padilla's case, people are claiming he didn't have a real plan, that he's a nobody. Maybe he is a small fish, but Padilla still received $10,500 bucks after getting approval from his handlers in al-Qeada. He is jobless, yet managed to travel around the world. I suggest he had plans already made and a target or targets selected with his possible co-conspirators, before he even went overseas to speak to the higher-ups. And whatever he revealed to them was sufficient to get them to provide him with $10,500 to get started, above and beyond what he was already obtaining to provide for himself. If the pattern holds, he or his group probably has financial sources here in the states, and perhaps women and fellow mosque-attendees who can serve as money 'mules' or as go-betweens locally, opening accounts, snatching credit cards, and purchasing or obtaining items while the men try to be stay out of suspicion's way most of the time. (One of the suspects nabbed early on after 9/11 here had written a check on woman's account; the woman supposedly worked at a charity in Washington DC but was long gone by the time they tried to track the account info down.)
Also, if the pattern holds, it isn't neccessarily the brightest terrorist-types who do the international traveling and courier work to and from the al Qeada handlers.