Self employed Affidavit of Support I864

[rgubernat]

I am self employed engineer with enough income to file i-864 sucessfully. I have 2 questions

what "evidence" of self employment is required aside from schedule "C" on 1040 tax form? Do I need a letter from myself stating that I work alone?

Also are all of the 1099's from payers required for all 3 years? One year they were not issued by the payer?

Thanks