Run.
Away.
Fast!
Unless you want a 24/7/365 job for life, full of patchy, unreliable equipment, maintained by anonymous strangers with varying skills and time zones. Even then they will resent paying you a living wage to support free open source software.
Go join a monastry. A quiet life, peace, and a safe place to sleep. Full of prayer and no anxiety.
Oh, as a property developer, make your showers actually waterproof, paint the tops of doors, all plumbing to be leakproof and temperature controlled to prevent scalding burns, make sure all floors are actually level (including the car park) so the wheelchair doesn’t roll away while you are not looking, put your braille signs at elbow level in the lifts so wheelchair users can actually find them, and put vinyl, not carpet in the passageways so the guide dogs are not distracted by strange smells when the janitor spills garbage by mistake and hopes nobody notices after he has cleaned up. Do not use gaudy or dull colors for paintwork, and make the parking spaces wide enough so you can open a door fully, side and back, and leave enough room for ramps, and allocate spots for carers and visitors too.
Go out in the sunshine, watch the kids play and happily laugh in the playground you thoughtfully provided as they play wheelchair football, and watch the pregnant moms pat their tummy as they sit in the park chairs, resting from their daily walk and care for the new generation to be. Yes life can be good, and with the right equipment, empowering for those with challenges not everybody faces.
Up front costs can be daunting, and service/maintenance/repair funds often come from seperate and restricted allocations. Put in the most robust equipment you can source. Don’t skimp on stringing it together with robust software that is user friendly and intuitive to use. Sadly, HomeAssistant may not meet those expectations, built by amateurs for people that enjoy fiddling and customising it. Life is too short to be distracted by Zigbee communication errors, disappearing devices after each monthly update, and randomly rebooting Raspberry Pi’s.
You are in the building game, not an open source developer, or 24/7/365 tech support. Let each professional specialize in their own field. Call in the experts and trust their advice. Don’t get distracted or sidetracked.