Once of the common mistakes Buyer's agents make when selling income property, whether it is a duplex or 20 units, is forgetting to make sure an important clause is in the contract. That clause should say something like:
"Seller agrees that they will not terminate, rent, evict or lease any units without written approval of the buyer"
The idea being that during the 60 days or so that during the 60 day transaction, the seller does not change the rental or income makeup of the property. It is quite common for sellers to represent 100% occupancy, then during the transaction, fill the place up with phony tenants ....frequently with no deposits. Or forget to tell the Buyer that 1/2 the tenants are not paying their rent and have been given notice to vacate.
And, if you suspect the seller might have done this (also quite often) BEFORE they listed, it is critical that you get a Tenant Estoppel from the tenant to make sure what is represented in the disclosures regarding income, and outstanding repairs is correct.
Just a little heads up!