Do they have to provide a screen door?
General regulations say no; they don’t have to provide one but it can vary from state to state. Also depends if there was one previously installed and was damaged therefore removed, never replaced. If there used to be one there then yes they need to replace it. You could simply ask the apartment manager. Little ones and a balcony? DON’T MIX! A sreen will not prevent the little ones from eventually pushing through it. NEVER EVER RELY ON SCREENS FOR CONTAINMENT!!! Keep it locked and buy a battery operated door alarm. Once they are able they’ll be able to open it and get out on the balcony. With the alarm you’ll know if that door is open even 1/2 an inch with a loud siren. Their inexpensive (10- 12 bucks) there battery operated and a since to install I have little ones and that alarm has been my second set of eyes. Although direct physical supervision cannot be ignored they(children) move from room to room with lighting speed 😉 Something like this