building access system - build site from scratch

Problem I have is that of contractors attending buildings to undertake works, regular inspections for safety by outside contractors. Building owner and remote manager want to record these access situations as they are not always by appointment. Need a QR based registration system linked into data base to then record not only who attends but for how long, some detail, sign out and brief report (optional) with capacity to upload photos as part of the registration sign in or out procedure. so the project will involve (but not necessarily limited to) : - need a manager access and registration page - linking to data base of his buildings only. - QR code linking to a specific building reference # - capacity to collate data for each visit - ability to download the data for reporting purposes to owners and managers - billing system automated for annual billing - preferably using DEFT type reference and receipt process. I've started mapping the processes required and am ready to move forward with a developer interested in pursuing this project. look forward to some advice and assistance.