I work in a DoS passport processing facility.
You can take your own passport photos at home, so long as they are printed on a proper printer, and taken on a white background.
Take one against a white painted wall in your house, thats what most people do.
The website has the size specs that the photo must be.
If you have a shitty printer, you can just edit the image down to that size, then bring it to walgreens and let them print it for 19 cents or whatever.