I could put you in contact with an experienced architect in the Chicago area if you'd like a more in-depth explanation on the topic specific to my area.

We recently hosted a  Watch Party in our Facebook page with 3 prominent attorneys in NJ regarding this topic and many others affecting landlords.

It's a great way to expand your current property or demolish the existing structure and build a whole new complex of units...Best of luck and be sure to call the city and check local zoning laws with a trusted attorney or architect/consultant.

@Alejandro GarciaInspections, due diligence on the property, decide if you are leaving as is or adding square footage, invite GC's and or subs to come in and quote for work at the same time as inspections so you aren't being rude to the occupant and respecting their time, invite architects if you are modifying anything, also invite them if you are converting the garage into an ADU, if you are terrible and design, find someone who isn't, most GC's are so don't rely on their sense of design.

Welcome to commercial real estate, where it takes $100 to make $1 :)That's how I handle smaller commercial tenants, the big ones don't care about that stuff and have engineers/architects to understand what the space is capable of from the get-go. 

Seek out Civil Engineers with landscape architects on their staff or develop a relationship with an L.A. well versed in local codes. 

I would talk to an architect as they go through this process often and are familiar with the submittal process. 

Without a couple of licenses under you it is impossible to take notice by anyone,  Many architects carry PE license also with a more technical background.

Assuming your plan fits in the current zoning you then have to have plans drawn up by an architect so you can get a building permit.

I spoke to a family friend of mine who is a local architect last night.