Membership in the credit union is voluntary and is open to all citizens bound by with joint work or residence, who wished to create a credit union to use its services and are willing to take on relevant commitments and responsibilities. In the U.S., credit unions have a clear organizational structure. All credit unions belong to one or the other parent credit union (there are 35 of them in the U.S.). Typically, donor contributions to the credit unions are targeted and used in the same statutory requirements and restrictions as the Mutual Financial Aid fund as a whole. Specialization of credit unions to provide financial services to its shareholders requires a particularly strict regulation of membership and acceptable activities. Credit unions base their activities on savings of shareholders, their shares and savings contributions, which make up the fund of mutual financial assistance - a source of cash loans to shareholders.