Duplex Not Delivered Empty

[Glenn Goodman]

Longtime lurker, first-time poster.

I'm an investor with two single family homes (a 2BR/1Ba and a 3BR/1Ba) in the small town I grew up in. I'm looking to buy a property in the city where I live now (about an hour away) where rent prices are much higher. I found a duplex with 3BR/1Ba on the first floor and 2BR/1Ba (with a bonus finished attic that could be a BR) on the top/3rd floors. The property is listed at $199,999. There is a pending offer on the table, but the buyer wants the seller to deliver the property empty. Apparently, at least one of the tenants has lived there for 24 years. The rent is grossly underpriced at $1,285 total for both units. The 3BR should be at least $1800 and the 2/3BR should be around $1400. 

Is this a red flag that the seller won't deliver the units empty? Or are they just being cautious not to end up with an empty property that might not close? Thanks in advance for any insight.