I too have found that very handy and have used it a number of times, if it was just some fixer, maybe a box of paper of developer then taking the carriage it indeed worked out cheaper, as far as opening a shop, If only I had the time, I am too busy with my photography business, I am the only remaining pro photographer in the Channel Islands, as far as I know, still working with film and working in Black and White and it keeps me busy, people over here like what I do and keep coming back
Richard