What is the ruling on depositing money in a bank as a certificate of deposit with interest for a person who is unable to work due to health reasons or old age, has no source of income, and uses the returns for living expenses?

If a bank deals with usury, it is impermissible to interact with it. The fact that a person is unemployed and lacks a source of income does not justify dealing with usury. The alternative is to invest money in a permissible investment, or to deposit it in an Islamic bank so that the profit may be lawful.