This is a very frequent question.
Photo copy is fine, in fact you should just have a copy of the return, IRS has the original.
Better yet get simple transcripts from the IRS.
http://www.irs.gov/faqs/faq1-6.htmlQUOTE
Are the Affidavit of Support forms required to be notarized?
No. The sponsor just has to sign the form. You should know however, when the sponsor signs an Affidavit of Support form, he/she certifies that the information provided, transcript and/or photocopy of tax documentation is true and correct, under penalty of perjury.
http://travel.state.gov/pdf/I-864GenInfo-FAQ-Final.pdf