I am a 72-year-old widow living comfortably on a $100,000 estate invested entirely in bank ceritificates. One of these certificates will expire shortly, and I am wondering if transferring $25,000 to a GNMA (Government National Mortgage Association) certificate would be wise at this age. - M. W.You sound like an excellent candidate for these ''Ginnie Mae'' certificates. Issued by GNMA as a means to provide money for the housing market, these certificates are backed by the full faith and credit of the United States government, which means the principal is fully protected. Yields on Ginnie Maes are usually quoted on a 12-year basis; throughout that period you receive a check every month. For $25, 000, individuals can buy shares of a Ginnie Mae pool from offices of most major national brokerage firms, as well as many regional brokerages. It is sometimes possible to get into special pools for $15,000 to $20,000.
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