12. Net Earnings From Self-Employment

You may have to pay income taxes on your benefits if your income is over $25,000 (single) or $32,000 (married - joint return).

So you plan on receiving both SSI and Social Security retirement benefits?

Assuming you're discussing retirement benefits, note that only your wages count toward Social Security’s earnings limits.

Your age is also a factor here. If you were born January 2, 1943, through January 1, 1955, then your full retirement age for retirement insurance benefits is 66. If you work and are full retirement age or older, you may keep all of your benefits, no matter how much you earn. If you are younger than full retirement age, there is a limit to how much you can earn and still receive full Social Security benefits. If you are younger than full retirement age during all of 2009, we must deduct $1 from your benefits for each $2 you earned above $14,160.

See here for details : http://www.ssa.gov/pubs/10069.html

There is something called the "The Windfall Elimination Provision" which may affect you.

The Windfall Elimination Provision primarily affects you if you earned a pension in any job where you did not pay Social Security taxes and you also worked in other jobs long enough to qualify for a Social Security retirement or disability benefit.

See here for details :
http://www.ssa.gov/pubs/10045.html

Yes, there's a good chance you can receive more from your Social Security retirement benefit.

For example, I used the following calculator :

http://www.ssa.gov/OACT/quickcalc/index.html

I plugged in your birth date of 6/1943, and used a 1997 wages of $30,000. Based on this, your estimated retirement benefit would be $1,457 per month.

If you use the above calculator you can change the wages and other parameters.

There are other calculators here :

http://www.ssa.gov/planners/benefitcalculators.htm

So I would contact Social Security directly to inquire about retirement benefits.