now a days immigration is taking forever to even issue a green card because of the long lines at FBI deptt
It all depends on the circumstance. When one comes on a fiance visa he will get a green card within 3 months after marriage. But if a person marries a US resident after staying here illegally, it will take 2 years or more, specially if that person overstayed the visa. The INS checks into everything.
A person I know overstayed his visa and after returning to Poland they issued him another one by mistake. So now this guy is back in the US illegally again, he does a fake marriage to a US citizen, the INS finds out about him overstaying the first visa, and wants him deported. Now his US wife has problems because they want to deport her with him. So they get this immigration lawyer and boy oh boy, what a mess when you try to help someone by illegal marriage.
So don't ever marry anyone for money. If you must, do it only because you love that person.