Including a diagram of apt layout helps sometimes.  

Your current space could also be more than you need or have  a bad layout making the move more optimal to another unit in the center.   9.

I think in this context if you follow the advice received above and just calmly and systematically lay out your case, relying on supporting documentation as you go, then things should be fine.

In my earlier response, I did not intend to imply there is any reason to eschew stacked duplexes, triplexes - we have a couple and, as @Matt Geerts points out, no stairs on the ground level provides the opportunity to create an accessible unit for those in wheelchairs or other mobility issues {Matt, might consider this ... designing with wider hallways and doorways (36/38") and a more open bathroom layout (perhaps with walk/roll-in shower) is simple when building new or doing a major renovation.} and makes your unit appealing to new categories of tenants (those with disability and aging Boomers are but two).That said, when looking at an older residential building {i.e. without an elevator}, my preference is still for side-by-side units over stacked.

@Vanessa Perez it sounds counter-intuitive but hiring a REALTOR can actually result in more money, not less.

It's pretty intuitive and free. 

Don't lay out your whole offer in your mail piece, instead give them a compelling reason to drop everything they are doing to call you right now.

The property has a confusing layout with strange historical uses and requires significant creativity and investment to get all the units ready to go.Major rehab:knob & tube electrical, heater is 100 years old and not working, 4 bathrooms either have all fixtures missing or are in tear down shape.

If you accidently kick over your paint can a clean work area will clean up easier then a cluttered area.good brushes are worth their weight in copperbecause good brushes offer better coverage better coverage means less time.if a friend stops by to watch ask them to remove or reinstall the switch plates this will save you time later so you can get back to the game.Take your time. ok sounds counter intuitive lazy people want to be done faster right?

Depending on the layout of your 18 units perhaps there is a central courtyard you can just place one of these in the middle as a deterrent.