If mom-and-pop can't cope with the responsibilities of being a landlord they should sell up to someone who can, not expect to be let off the hook when they make someone's life a misery.
Also, if a property did have an ADU in it, and someone was renting it out, a prospective buyer who didn't want the responsibility of being a landlord would find that a huge negative, which would decrease the value of the property to the existing owner, and provide additional incentive to avoid constructing the ADU at all.
If I were looking to buy a home, then a home with a tenant-occupied ADU is less desirable than an otherwise identical home without the ADU. The hassle and risk outweighs the rental cash flow.
Landlords generally can't suddenly increases rents. It happens only at the end of lease, and everyone knows when the lease is going to expire, and you have 1-2 months at a minimum to negotiate the lease renewal. If a landlord suddenly increases the rent by a lot (although most leases, or city laws, cap max rent increases), it will be disruptive to you. But your worst case scenario is to move to another market price rental in 1-2 months.
For a landlord, a tenant who stops paying rent, damages the place, etc is a much bigger financial and logistical risk. In most places, it's a lengthy, high-effort process to evict a bad tenant even when you have documented evidence. This is a very difficult scenario for a mom and pop homeowner, hence rules should be different for them at least, compared to large corporations.
And in your good (but overzealous) intent to protect the general majority of good tenants, you're not realizing that thenet result of the above is:
- Landlords are hesitant to rent their places or ADUs unless they really need the money, which reduces supply, thus increasing rents
- Landlords have to charge higher to account for the risk of a bad tenant, as well as for a complex eviction process, thus increasing rents
Rent control like laws benefit current renters, in their current properties, while harming both landlords and importantly for your pov, future renters, including current renters in their next rental. But since this cost is diffused to the future, it's easy to ignore and forget.