Pull the domain's organic traffic trend in Ahrefs or Semrush. A domain with a domain rating in the 50s but near-zero organic traffic is a strong sign the authority was built artificially, not earned through content people actually visit.
Check the outbound link profile. If a site links out to dozens of unrelated niches — casino, pharma, essay-writing services — in the same week, it's operating as a link marketplace, not a publication.
Look for a real editorial presence: bylines, an about page, other articles that aren't obviously written to host paid links. A site with none of this is likely a shell built to sell links.
None of these checks are exotic — they're the same criteria any competent in-house team would apply, and the same ones we apply before pitching a domain to a client.