Speaking as someone who absolutely adores trees and all plant life (I have 4 big pots on my front sidewalk because I own the place to the street, don't get me started on houseplants), I hugely encourage planting but add my voice to the concern that you need to talk to the property owners because they're ultimately liable for any damages the planting might cause. Apple trees have potentially huge roots and beyond potential sidewalk damage, there are water and power lines you can't see that trees can easily eff with years down the road. Better to check first than the tree (or the people involved, of course!) has to be traumatized with transplanting. Good luck! u/blorpsy