Multi Step Form

What is the best way to create this form. I think it is common but can’t find any good ideas or docs for this setup.

I need 2 step form, User selects common data on first page like address of a building, on a second page he needs to select apartment and put in name of a person leaving in the building, this data needs to be added until all apartments in a building have names. The tough part it is not known how many apartments in the building, some might have 2, other 120. How do I add data in this way. I have app setup in 1 form now, so user needs to type address every time he needs to enter apartment, I am looking to make it a bit simpler and faster

I am not an experienced form builder.

However, this MAY help you: