Things to look out for when buying and planning to duplex down

[Ryan Monty]

Hi all - I'm considering buying into a house hack situation, a 2 or 3 unit (most likely 2) building that has the potential to duplex.  I would live in the duplexed unit and rent the other(s).  I'm also open to duplex up, but I'm assuming this is likely more difficult.  Please correct me if that's an incorrect assumption!

Obviously I'd love to keep the costs to a minimum, so I"m wondering what things an experienced eye would look out for in the showing/buying process to identify potential problems or advantages a property may have compared to other options?

It seems like finding a building that already has an "in-law" unit in the basement is a great start.  It's already finished, so I'm assuming one of the main jobs needing to be done is building the interior stairs.  It's not very important to me to add an additional bathroom down there if there already is not one.  Nor would I care to add a kitchen.  I would just like additional comfortable living space down there, and probably a sectioned off area for the laundry, etc.   

Also, what would a ballpark be on this work if all I needed to do was build the staircase and possibly add some walls?