Permanent total disability has the same base rate as TTD benefits with a 3% cost of living added in for each year after the accident. But the TTD rate has to be correctly calculated.
So if your accident was 12/31/08 we would look at you earnings from all employers for the 3 months prior to 12/31/08, so basically 10/1/08 to 12/30/08. You add the earnings and divided by 13. This creates a base AWW (average weekly wage). 2/3 of the AWW is your TTD rate. The law requires that income be reported to the IRS before itcounts as income. This avoids contractors getting 1099's and not paying taxes, then claimant workers compensation. But contactors often have expenses affiliated with earing that money so if the 1099 says $4,000 but you reported $2,000 in materials cost, your income would be $2,000. That's why you have to look at schedule C.
It is the money received during the 13 weeks prior to the accident. If the work is seasonal or sporadic there are methods to average your earnings.