We suggested they start a business and buy through the business name but aren't sure about that either. 

Do they provide a Perpetual Cost Segregation Evergreen Annual Review to find annual expenses from dispositions, additions, favorable changes in tax laws?

So, I would suggest to get with a realtor to help you find the specific neighborhoods that might fit your needs.  

I strongly suggest you create an LLC for each investment property you have that way if the loan goes sideways and they have to foreclose, they can only go after the specific asset and not your whole portfolio. 

Two things I'd suggest is to keep house hacking and dollar cost averaging. 

Full review properties and solid reserves.

I would suggest that you check out some local meetup groups in your area.Good Investing...

Current legislation is trying to undermine that stability, but with proper guidance (I suggest hiring a good PMC unless you're an attorney and you know all the current landlord/tenant laws) you should do well. $50/month cash flow is fine. 

The height of each unit is about 8ft I believe.let me look up the sqft I believe it's a standard sized lot for chicago so about 3000 sqft Neighborhood is starting to see some nicer units rents are all higher but it's leans more low income I have a contact that is going to ask the alderman if I could build a separate unit and have the original as an adu architect suggested extending it as they believe it would be easier to get approval than a separate home

I highly suggest teaming up with a broker who you'd want to build a relationship with and truly understands the ins and outs of different underwriting guidelines for DSCR loans.