The money is to be repaid in installments which usually combine principal and interest payments. Similar to bonds, these securities are backed by a share in a pool of home mortgages insured under the National Housing Act. The securities pay interest and a part of the principal each month and, if home owners prepay their mortgages, may pay out additional amounts of principal before normal maturity. They trade in the bond market at prices reflecting current interest rates. These are open-end funds that are not listed for trading on a stock exchange and are issued by companies which use their capital to invest in other companies.
Mutual funds sell their own new shares to investors and buy back their old shares upon redemption.
Capitalization is not fixed and normally shares are issued as people want them.