If you are doing electrical, plumbing, and shifting of the physical layout, then get a licensed contractor.As an example, i do items like tile but without a license could not do your electrical (even though i know how to).Hope this helps,Matt

Made it easier for plumbing and hidden with a cabinet.

It will cost more for the gas plumbing and all related items. 

There were some headache repairs such as a plumbing leak that had been there for a while, some roof issues, and poor bathroom fans that contributed to common mold in our area.

There were only 10 units originally, and I added an 11th by using existing plumbing/rooms in place.

This deal would have a lot of updating and all new appliances, furnace with central air, water heater and new plumbing in the entire house 

Working with a contractor, we put together a scope of work totaling approximately $85,000 to fully renovate three units, including the addition of one bedroom, and complete necessary CapEx mechanical repairs including updating many plumbing fixtures, and updating electrical fixtures and systems.

This lead to extensive change orders and changes in scope, due to unforeseen code issues with electric and plumbing.

. $25-30/sf for a lower end refresh.I have not designed the garage space for the ADU yet, but when I do define the scope, it will include all new electrical, plumbing, HVAC, custom windows, insulation, 1 full kitchen and 1 full bath, exterior paint and a couple of new garage doors.

There's a crawl space that's inaccessible because there's plumbing that goes across the door but likely there are termites there as well.