Found it: To qualify for benefits, you earn "credits" through your work - up to four each year. This year, for example, you earn one credit for each $1,320 of wages or self-employment income. When you've earned $5,280, you've earned your four credits for the year. Most people need 40 credits, earned over their working lifetime, to receive retirement benefits. For disability and survivors benefits, young people need fewer credits to be eligible.
So I'll pick up 1 qtr per year.