Disregard the drawing app idea - There are many on YouTube.
The Zillow style app though would be very interesting to have demo the ability of two accounts interacting with a user-created database object.
So, one account creates a database object in a universal list (equivalent to me creating a new home listing) which the other user can interact with in a different way than the user who created it.
The creating user might have the ability to edit / remove the post and it’s attributes, while the interacting user(s) would have the ability to interact differently (request an appointment, send payment, etc.)
It could be simplified for sure, but the concept I think is very common, yet one I haven’t been successful finding a comprehensive guide on.