I'm 70 and have collected Social Security since age 62. Do I pay in again if I return to work? -- Mike Mobley, Sacramento, Calif.
Yes. Even though you're already collecting, you'd have to pay Social Security taxes: 6.2% of your earnings on wages up to a cutoff that will be $117,000 in 2014, says AARP's Jonathan Peterson, author of Social Security for Dummies.
Some good news: Because you are beyond your full retirement age of 66, working won't reduce your benefits. (In years before your full retirement age, benefits would be cut by $1 for every $2 you earn over an exempted amount -- $15,480 in 2014 -- although you'd get that money later as a higher benefit.)