Landlord here, how do you find a plumbing contractor who won't gouge tenants?

[nevillelongbottom]

I own a small duplex near California Ave and the tenants just reported a slow drain in the kitchen that's starting to back up. I live out of state now so I can't exactly drop by and snake it myself. I've used a couple of big name companies before but they always seem to find a way to turn a simple clog into a four figure job, and my tenants are the ones stuck dealing with the sales pitch. I'm looking for a plumbing contractor in Palo Alto who is honest and doesn't treat renters like easy marks. Has anyone here been in this situation? How do you vet someone from a distance? I don't want to be cheap and ignore a real problem but I also don't want to pay for a whole repipe when it's just a hair clog. Any advice on what to ask over the phone or red flags to watch for would be really helpful because I'm flying blind here.