Looking to add additional legal unit to multifamily

[Yesenia Valdez]

Hello Bigger Pockets Community!

My name is Yesenia, born and raised in city of Chicago ( little village), I am new to this community and excited to learn and share all things real estate. 
I started investing end of 2019 with my first multifamily purchase in the Lawndale area that I was able to sell for profit and purchase a 3 unit building with unfinished basement in 2021.  I currently own a total of 6 rental units ( 2 multi family, 1 condo).

My goal is to convert the basement of one my multifamily properties into a legal 4th unit. The unit would need ground up work, plumbing,  concrete,  architect plans etc. Finding the right financing strategy is my biggest roadblock right now.Im also in search of architects and GC's who have experience working with the City to work on this project.

P.S.  does anyone have experience converting basement to legal unit ? If so, any tips to keep in mind or advise you would give ? 

Thank you in advance!
Yesenia