Your proposed plan is a good option.  

Will they still perform under terms that may attract a typical investor?

Like @Michael Baum and @John Underwood said, this is a highly competitive area and I don't typically recommend going into a neighborhood that isnt a resort.

I use the typical rules of thumb of 5/5/5.

Note owners do not have vacancy, tenant turn over, typically take better care of the unit than tenants so have reduced maintenance/cap ex compared to a LL, and in many markets owners have reduced property tax compared to non owner occupied.  

I have a tenant who has never been able to make rent on time, they are typically making partial payments throughout the month to get current on rent before the start of the following month.

Make sure you know the value the ADU will add to the property before building the ADU. 2) the financing on an ADU is typically far worse than for initial investment property acquisition or is often not leveraged (HELOC, cash out refi, etc).

We have a multi family rental unit which uses oil for home/water heating.Our tenants are responsible for purchasing their own heating oil.We are trying to figure out a way to determine when/if our tenant is running out of fuel.Our maintenance person has communicated that one unit has repeatedly run out of fuel, creating an increase service cost on their boiler.I know there are WiFi options to meter usage.

If those options are not allowed then you must serve them notice to QUIT.

Should you still need assistance, we are a Mortgage Brokerage and have specialty new construction loan options for me.