I don't have "stock" photos that I use, but I don't always update the pics, I'll just send the ones I already have. Depending on the person I'll do more or less. If it's someone wanting the cheapest animal I have "just for a pet", I do a lot less. If it's someone wanting a potential breeder, I get pics, because animals aren't all equal. I could sure tell you if I saw a pic of a smooshed face blocky kit, and get a rat faced wedgey one instead, I'm sure others could too. I'll sometimes send an older pic I already have, especially an adult animal, they're not changing all the time like a kit will.
Usually if a person I don't know, or know of, starts asking about the most expensive chins I have available without giving me any background on them, I don't put much effort into it. A pet owner will usually tell you about themselves, especially if they're going to spend a lot of money.