Is there a certain amount that I must invest to become eligible for a green card through investment?

Generally, investments that can form a basis for an immigrant visa (to become a Lawful Permanent Resident, to get a "Green Card"), must be $1,000,000, although a minimum of $500,000 may be sufficient for investments in designated economically depressed geographical locations. There are many additional requirements for success in this type of application, including documentary evidence of the legitimate source of the invested funds, the placement of the funds at risk, the expected employment of American workers, etc. It would be a mistake to initiate this type of immigration application (or even to select an investment with expectations of the investment meeting immigration-related requirements) without engaging an immigration attorney to provide legal representation in this complex type of case.