A lot of those companies will find something to remediate when nothing real exists. 

@David Frandsen hi, I am converting a existing garage to a 2 bed ADU in Vista

- what kind of existing slope/grade?

It is a 6-plex but with the existing building size, I could easily add 2 units, but cutting the size of the larger units. 

Not knowing if there are tenants or if it is empty, the condition, if there are any code violations existing, if you are assuming a company name that holds the property and if so, the standing of that entity as well as contingent liabilities, what kind of municipal requirements there could be like registration as a landlord in that jurisdiction, or of any other details, I really can't tell you what you need to do first.

Since these building's already exist they are all an existing 'non-conforming' use, the four plex may just not be able to continue in it's non-conforming utilization as is.

Master meter utilities are the bane of any investors existence, unless you somehow figure out a system to monitor and/or control usage. 

Make sure to review the existing leases as you'll be obligated to those terms unless you have them sign a new lease.

Our plans have changed and we intend to split the property in half and build a new home on the new property, and rent out our existing home.

Just purchased a new property and can’t decide if I should raise the rent with the existing tenant.