Hello!! and Welcome!!
I am in a 5th floor condo. in DC....in the back of the building.
I got one of the Purina Second Nature Litter pans and put weewee pads in it instead of the doggie litter.
PurinaŽ secondnatureŽ Housetraining Solution
I also use the weewee pads from PPE Pet Supplies.
I was using Drs foster smith pads, but I like these much better.
14 COUNT - Clean Go Pet Puppy Pads - Steals & Deals
I also purchased a diaper genie.
I got that tip from someone here.....
It has been working great!!
Good Luck!!