Sorry I have been a bit slow in responding to this, but I do not think that one word, "photographer", can be described as a confident statement. It may well be a generic job description inserted by the enumerator in place of a more lengthy description given by the subject. Indeed this is borne out by the description used by Begbie when his first child was born in 1865; in the "profession" column he describes himself as "photographer's assistant". As this document is actually signed by Begbie I think that we can reasonably take this as an accurate statement.
Given that McGlashon was an active and experienced photographer I think it is very unlikely that he would have entrusted expensive equipment and indeed his own reputation (it is McGlashon's name that is on the photographs) to a youngster with no previous photographic experience.