Question about purchasing 4 of 6 unit townhome buliding

[Steve Balinski]

Hello Biggerpockets followers.  I have an odd scenario on a "property" i just had an offer accepted on.  The building is 6 units, but the seller has it listed as 4 units, in 1 listing.  Its 3x 3/2's and 1x 2/2

My question is what concerns/ complications/ cons does this propose, if any?  Its a rare scenario, but i'm just not sure if that matters.  My main concern is resale, but if the numbers work well, why couldnt I do the same thing and sell the 4 units.  The other 2 units recently sold in a week or two.  

Thanks