The client could have software installed which could capture the password and use if after you leave.
Great point. Definitely overlooked this factor, but I highly doubt that anyone who lives in my town has the know-how to do those things, though, taking that into consideration, it wouldn't be good practice... just in case. But really and seriously, no one in my town knows how to do that crap and if they did, they would know how to fix their own computer 99.9% of the time.
And why would you be accessing the business router from a clients PC and not the business workstation? Strange??
It's just convenient and if you are 100% confident in there being no risk, why not? Why am I confident? See above reply to quietman7.
They probably charge and make more money doing "house calls".
I'm not sure what you are trying to get at. House calls are not a service we offer.