Inheriting tenants - No Lease/No Estoppel - Walk away?

[James S.]

I am looking to buy a 3 family, there is 1 tenant paying under market rent on a month to month.

Seller's lawyer is advising that since this is a estate sale, seller has no right to request estoppel certificate. 

Can I request a estoppel certificate myself from the tenant during inspection/prior to closing? Can I have my agent do it? Is it even worth it to go forward with this deal if I cant get the estoppel?