What is the light levels in your friends home? Low light? Medium? A low to medium light level plant would be fine if they don't get much sunlight due to buildings in the way. Chinese evergreen, ZZ plant,deffenbachia, pothos, spider plant. IF they get plenty of sun then your choices increase.

Tom

If you are talking indoor plants, New Yorkers are in to all kinds of things, including orchids. And some of them have terraces where they grow things and even backyards. Most of these are shady but I've seen some gorgeous pictures of shade gardens in NYC. It's zone 7 so they can grow some things I can't but hostas (no deer down there), astilbe, martagon lilies, heuchera, kirengeshoma, tricytris.. lots of possibilities.

My mother has overwintered perennials such as boltonia, lavander and rosemary on her balcony in pots. The hostas survived too, but they don't enjoy the drying winds of balcony life.

Thank you to all of you who responded. I really appreciate you taking the time! Best regards!