The banking community is small and very interconnected in WNY so shouldn't have a problem getting connected to someone that can help.

Quality solar installers will handle all of the system design, equipment purchasing and delivery, permitting, rebate/REC/interconnection agreements, warranty the system for 20-25 years and handle any manufacturers warranty issues as well, but not if the equipment is from a random manufacturer that they don't work with.

We also use the combo smoke/carbon wireless interconnected ones so when one goes off they all go off on tenant turns and new acquisitions and we use the non wireless ones for existing units, but still the combo smoke/carbon.We also make sure to test them when moving in a tenant, in front of the tenant and have them sign a separate smoke detector addendum to the lease that states they alarms were working at move-in, they understand they are not to remove and they are responsible for the batteries and maintenance. 

The edges interconnect via built in glue strip.

When doing almost any sort of rehab, most building departments require you to add hard-wired, interconnected smoke detectors IN every bedroom and in some other locations and some of those have to be combo smoke/CO detectors.

The situation that would make this conversion the most difficult and expensive is if the branch supply plumbing (hot and cold) for each unit is inter-connected inside the walls and/or slab foundation for each unit.

I use the hard wired interconnected ones when possible.  

I've heard of them requiring things from investors such as grading driveways or "requiring hard-wired, interconnected smoke detectors".

If you can find one that was built before 1972 and has had the basement suite since before then, it could fall under grandfathered rules, which as long as it has windows of proper egress size, interconnected hardwired smoke alarms, and a private entrance, doesn't require much else in the way of upgrades or zoning.

Old Victorian house converted into 3 - 5 units) is the cold water is frequently interconnected between units.