Question: How long does a member of congress have to serve to get a pension?

Disambiguated questions and answers:
context: No context provided
question: How long does a member of congress age 62 and older have to serve to get a pension?
short_answers: 5 years

five years

context: Congressional pensions, like those of other federal employees, are financed through a combination of employee and employer contributions. All Members pay Social Security payroll taxes equal to 6.2% of the Social Security taxable wage base ($128,400 in 2018). Members first covered by FERS prior to 2013 also pay 1.3% of full salary to the Civil Service Retirement and Disability Fund (CSRDF). Members of Congress first covered by FERS in 2013 contribute 3.1% of pay to the CSRDF. Members of Congress first covered by FERS after 2013 contribute 4.4% of pay to the CSRDF. Members covered by CSRS Offset pay 1.8% of the first $128,400 of salary in 2018, and 8.0% of salary above this amount, into the CSRDF. Under both CSRS and FERS, Members of Congress are eligible for a pension at the age of 62 if they have completed at least five years of service. Members are eligible for a pension at age 50 if they have completed 20 years of service, or at any age after completing 25 years of service. The amount of the pension depends on years of service and the average of the highest three years of salary. By law, the starting amount of a Member's retirement annuity may not exceed 80% of his or her final salary. There were 611 retired Members of Congress receiving federal pensions based fully or in part on their congressional service as of October 1, 2016. Of this number, 335 had retired under CSRS and were receiving an average annual pension of $74,028. A total of 276 Members had retired with service under FERS and were receiving an average annual pension of $41,076 in 2016.
question: How long does a member of congress age 50+ have to serve to get a pension?
short_answers: 20 years
wikipage: Congressional pension

context: No context provided
question: How long does a member of any age have to serve to guarantee a pension?
short_answers: 25 years

Long answers:
knowledge: content: Congressional pension is a pension made available to members of the United States Congress. As of 2019, members who participated in the congressional pension system are vested after five years of service. A full pension is available to members 62 years of age with 5 years of service; 50 years or older with 20 years of service; or 25 years of service at any age. A reduced pension is available depending upon which of several different age/service options is chosen. 
wikipage: Congressional pension

content: A pension (/ˈpɛnʃən/, from Latin pensiō, "payment") is a fund into which a sum of money is added during an employee's employment years and from which payments are drawn to support the person's retirement from work in the form of periodic payments. 
wikipage: Pension
long_answer: A pension is a fund into which a sum of money is added during an employee's employment years and from which payments are drawn to support the person's retirement from work in the form of periodic payments. For the United States Congress, as of 2019, members who participated in the congressional pension system are vested after five years of service. A full pension is available to members 62 years of age with 5 years of service, at 50 years or older with 20 years of service, or 25 years of service at any age.