As long as it comes back the same condition i pass to him, else he don't need return back the current equipment. (he just have to find an exact same one or better condition)
I have equipment which i don't mind borrowing, but i warn them the above phrase as i explain some of my equipment took me months to find them online. My ef 80-200mm f2.8l took me close to a year to see someone selling it at a decent price. (There isn't 1 except spare parts on ebay the last time i search it) My pentax asahi ghostless filter which might not worth more than 20usd took me more than a year before one appear on ebay!