Buying IG Account with Custom Domain as Original Email?

If someone is selling an IG account with the original email included but the OG email is from a custom domain the seller owns, what should a buyer ask or demand be included?

For hypothetical example, a seller is selling a business IG account called Jeff’s Golf Clubs, as the business is no longer active. The OG email for the account is, hypothetically, admin@jeffsgolfclubs.com instead of gmail.com or whatever else. The website of the company/email is parked via GoDaddy.

What does a buyer do or ask? Hypothetically, the seller could always take the account back no matter what if they had control of the actual email domain, right? What if the seller is offering the domain panel as part of the sale? Could the domain panel be used to pulled back and then the IG account pulled back?