I would take some time and calculate whether the warranty is cheaper than your separate "savings" from your rental income allocated to cover capital expenditures.

Typically those are built on both sides of the party wall with a single wythe of brick separating them.

Each unit is separately metered and I would like to get them to pay for electric themselves.

Specifically, this bill provides the park owner or management and homeowner of a mobilehome park may enter into a separate agreement which would grant the park owner or management the right of first refusal.There are approximately 4,850 mobilehome parks and manufactured housing communities in California providing spaces for an estimated 675,000 residents.

Would you be able to install a separate door somewhere that would get easy access to the older bedroom?

We do everything together and have separated tasks to become a perfect team.

Take an hour or two to education yourself on the subject.I cannot say if I would rent to them or not, as it depends on much more for me, such as: their pay (separate and together); their time on job(s); references; interviews; etc...

I recall there being a law in New York State that required separate meters if tenants were required to pay for utilities (which makes sense). 

I personally separate my rentals from my Airbnb because I buy in places that will make sense long term to a family and I create a cash flow almost passive income, on the other side I go to an area of town like near a hospital, college, downtown ETC... and rent there which in most cases will be CHEAPER then owning, I will not get the appreciation and some other RE benefits but Airbnb is not about that it's about cash flow and hopefully I buy right my long term rentals.

I would love to have a detached ADU, and a mother in law suite (basement) in a detached single family property to have 3 separate rentable units.