@ Michael Hicks
Currently, the one side is a 3/1 and the second side is a 2/1... Attic is only accessible via the 3 bed side currently. My thoughts would be to make the third floor a master suite for the three bed unit and have combine two tiny bedrooms into one on the second floor, yielding a three bedroom total for that side.
I thought about the floor joists as well. They are true 6" lumber so they may make me sister them worst case scenario. I have another unit where the building dept. didn't make me do anything with the existing joists. I would be rolling the dice on that portion, but thats not a huge cost.
I have never had to add sprinklers in anything residential at this point. I believe our code only requires that if there are three or more adjoining units so it is treated as commercial.
On the costs, the units are going to have to be almost completely stripped to the studs everywhere so my thoughts were now is the time to do the work and force appreciation. I plan to hold on to it for awhile... the area is really up trending.