Eligibility for award, commencing with the period after 31 December 1960, was established by DOD Directive 1348.7, dated 1 April 1966, and terminated effective 15 August 1974, per letter from Manpower and Reserve Affairs, subject: Termination of Eligibility for the National Defense Service Medal, dated 30 June 1974.
If you are single and under age 65, you can earn up to $9,499 in a year and not file a tax return. Should you be 65 or older, you could earn up to $10,949 and be exempt from filing a federal tax return. However, you may qualify for an Earned Income Tax Credit, which is refundable in cash to you.
Until you reach full retirement age, Social Security will subtract money from your retirement check if you exceed a certain amount of earned income for the year. For the year 2015, this limit on earned income is $15,720 ($1,310 per month). The amount goes up each year. If you are collecting Social Security retirement benefits before full retirement age, your benefits are reduced by $1 for every $2 you earn over the limit.