I'm far from a tax guy, but my (painful) understanding is that business taxes are connected to the owner of the business.If they are running some kind of retail biz or an operation where they have clients coming in and out of the facility / building they should have a liability policy, and you should as well.a CPA should be able to answer the tax question, and a RE attorney could advise on the liabilty issue.

It's practically impossible to install a grab bar in this bathroom without a complete remodel, but a handicapped toilet should just barely fit.Of course, it's hard to know during a rehab that one property might attract obese tenants, so pre-installing a toilet just for that reason doesn't make a lot of sense unless the property is near a diet facility. 

May they need to go to a care facility.

Actually, the more I think about it, CA landlords might want to start including a clause that says just that - the landlord is not liable for PG&E outages.I found the following from this website: https://www.stimmel-law.com/en/articles/landlord-obligations-habitable-premises-basic-california-lawThe Statute:In terms of residential leases, in order for a landlord to be allowed to place rental units on the market, the landlord must first ensure that all of the following conditions which make the building ‘fit for human occupancy’ are met: [Civil Code Secs. 1929, 1941]Effective waterproofing and weather protection of roof and exterior wallsWell-maintained plumbing and gas facilities compliant with law in effect at the time of installationWater supply compliant with applicable law that is capable of producing hot and cold running waterWell-maintained heating facilities compliant with applicable law at the time of installationWell-maintained electrical lighting compliant with applicable law at the time of installationBuilding, grounds, and appurtenances kept sanitary and free from debris and vermin at the time of rent or leaseSufficient number of receptacles for garbageWell-maintained floors, stairways, and railingsLocks conforming to code [CA Civil Code Sec. 1941.3]Dead bolt lock on each main swinging entry doorWindow security or locking devices for windows capable of being opened

(B) A restriction on the size and attributes of the junior accessory dwelling unit that conforms with this section.(4) Require a permitted junior accessory dwelling unit to be constructed within the walls of the proposed or existing single-family residence.(5) Require a permitted junior accessory dwelling to include a separate entrance from the main entrance to the proposed or existing single-family residence.(6) Require the permitted junior accessory dwelling unit to include an efficiency kitchen, which shall include all of the following:(A) A cooking facility with appliances.

So, go ahead and discriminate because someone is late, or smells of smoke, or has unruly kids, or never asked you where the laundry facility is (why don't they care? 

Looking into quasi-RE ventures, like senior centers/communities and care facilities that the government is least likely to mess with.

That can be tedious but the only way.Also ensure that your doctor or heath facilities you visit or plan to visit takes that health particular plan, before you sign up.Unfortunately, no one in either parties elected or running for office been able to fix health care in the US.

Exemptions include "Housing accommodations in which the tenant shares bathroom or kitchen facilities with the owner who maintains their principal residence at the residential real property.(5) Single-family owner-occupied residences, including a residence in which the owner-occupant rents or leases no more than two units or bedrooms, including, but not limited to, an accessory dwelling unit or a junior accessory dwelling unit."

Also I'd not over think it; Apartments are noisy, and as long as there are separate entrances/laundry facilities it shouldn't be too much trouble as long as you can figure out how to handle the separate utility billing to the tenants.