ETA a few days later - of course, please check with your own accountant as I am not in the tax biz in any way, shape or form...!
From www.ssa.gov (social security’s website)
Latest amount & QC explanation
The amount of earnings required for a quarter of coverage (QC) in 2013 is $1,160. "Quarter of coverage" is a legal term, but you may also see the term "Social Security credit" (or just "credit") used elsewhere. A QC is the basic unit for determining whether a worker is insured under the Social Security program. No matter how high your earnings may be, you can not earn more than 4 QC's in one year.
History
See historical series of earnings needed to earn one quarter of coverage, 1978-2013.
For years before 1978, an individual generally was credited with a quarter of coverage for each quarter in which wages of $50 or more were paid, or an individual was credited with 4 quarters of coverage for every taxable year in which $400 or more of self-employment income was earned. Beginning in 1978, employers generally report wages on an annual, instead of quarterly, basis. With this change to annual reporting, the law provided that a quarter of coverage be credited for each $250 of an individual's total wages and self-employment income for calendar year 1978 (up to a maximum of 4 quarters of coverage for the year). After 1978, the amount of earnings needed for a quarter of coverage changes automatically each year with changes in the national average wage index.
Determination of the quarter of coverage amount for 2013
The law specifies that the quarter of coverage (QC) amount for 2013 is equal to the 1978 amount of $250 multiplied by the ratio of the national average wage index for 2011 to that for 1976, or, if larger, the 2012 amount of $1,130. If the amount so determined is not a multiple of $10, it shall be rounded to the nearest multiple of $10.
From the day you posted this question - Edited: We need to work for 10 years (40 quarters) paying into SS in order to draw SS between 62 and 67. You also need to pay into Medicare. Maybe SS will be different by the time we are 67, but you can't be thinking about that right now, J.. You need to use today's rules to plan your life. It is also really important to pay into Medicare no matter what you think might happen to SS. You are smart to think about this.
Talk to your tax advisor about it. IF you are self-employed, you have to pay double the amount, since companies cover part and individuals who work for them pay part of FICA. There's a cap for paying SS, according to your salary, but you pay 2.9% of what you make for Medicare, with no cap.
Your tax advisor can tell you the real nitty-gritty here, but you can't just declare yourself self-employed, not make a profit and not pay into SS, and have it count toward your 40 quarters. If this were allowed, people would do it all the time and never pay in.
If you look at SSA.gov/oact/cola/QC.html, it tells you that you must have a minimum amount in earnings in any given quarter to qualify for SS credit, provided that you make a minimum amount of profit in one year. (Prevents people from making just the minimum in one quarter and then losing money the rest of the year...) Go to SSA.gov and search earnings/social security credits and minimum self-employment income.
I urge you to really figure out the Medicare part of this equation. I don't know the rules about how long you have to pay into it, but I think it's even more important that SS. (Just my opinion.)
Knowledge is power. Get the knowledge from profesionals who know exactly how this works.