As Ben suggested you probably do not want to start with the photo.net source tree. ACS was released from photo.net through roughly version 3.2 and therefore the photo.net site was kept pretty clean. But since then quite a few programmers of various degrees of experience with Web/db apps have gone through the photo.net code and done things without much thought, planning, review, or documentation. You'd be much better off starting with a clean ACS 3.4.x from ArsDigita or with OpenACS (the latter is probably best because of the existence of this community where you can get support).
