I got this during the Lakepoint Tower scenario where you have to get a lot of apartment dwellers. The Luxury one-bedroom apartments require cable television and I was able to fit 6 units per floor. You just have to build the units to get the achievement - they don't need to be occupied. Daycare Centers and some Restuarants/Pubs also require cable tv.
Luxury Studio apartments also require cable television and you can fit 7-8 on a floor depending on elevator and trash/recycle placement.
If you're just playing a regular game then luxury studio apartments is the way to go. Video Game Studios also require cable television so they are also an option.