Time required to vet new vendor's profile?

I'm finding that it takes much longer than I expected to vet each individual new vendor's profile - this includes checking rates for services, viewing the attached resume/CV, looking up the vendor's professional website/LinkedIn profile, contacting references, etc. How long does it usually take VMs to vet vendors? Which sections do you make sure to view versus ignore until needed later, when the vendor is already working with you?