Front Door Access for 6 Unit Building

[Brad Ehnert]

I'm currently rehabbing a 6 unit apartment building and am looking into doorbells and intercoms. Most multifamily intercom systems I'm seeing use phone lines, which just seems antiquated. Ideally I would install individual Ring Doorbells for each unit, but can these be connected to the same main door lock? Are there any other options like this? I planned on installing a keycode door lock on the front door so I can give access to contractors, mailmen, etc. 

Thanks.