Apart from getting in the country and finding a job, isn't that something that they could each finance personally, individually? Especially with a bit of credit, as they didn't have long-term credit rating concerns.
>> The 9/11 Commission stated in their final report that the "9/11 plotters eventually spent somewhere between $400,000 and $500,000 to plan and conduct their attack"
Still a non-trivial amount of financial support.