IF you’ve worked in a vets office or groomers I’d especially like your input on this

I’m trying to start a little business (not the most glamerous…its picking up pet waste lol) I have a few clients but of course could always use more. Several friends have suggested I try see if I could leave business cards at vets or groomers (or anywhere else doggie oriented) I know my mother used to do that years ago with her business cards, but I was wondering if thats allowed anymore?
If you’ve ever allowed this in your business, do you prefer someone use those little biz card holders? Or did it matter much?
I live in a smaller town, so word of mouth is about the only means of advertising here. Thanks for any input!
Aileen