I know the interest they get is taxable I would probably have to set up a LLC with them being equal partners.

Some lending programs are more or less (there are various programs) but in general 50% DTI is max.In order to ensure you accurately plan for your future mortgage its good to know up front how these situations would be affected and what borrowing power you will need when the come times to purchase this upcoming "condo."

I am new to REI, so I don't have a good agent to get numbers from and I don't have any Property Management contacts to talk to.Does anyone know where I can go, to get a feel for what I could rent a (3) bed, (1-1/2) bath, 1,200 sqft duplex in Twinsburg, OH for?

But some buyers that use seller financing don't take the same steps (taking title in their name and closing at a title company) because they don't know any better. 

Let me know if you have questions on funding and I will be happy to talk to you.Best,Jackson

Chicago has solid cash flow markets and many appreciating markets with much lower cash flow.Interest rates are significantly hurting cash flow, so in my opinion, this is a time where you have to settle for low cash flow, knowing that there are also tax benefits, debt pay down, and appreciation happening.  

He is wanting to give preference to cash buyer and I can do that but just want to know how this type of deal goes, etc. 

I know ultimately it's up to the town / marshal 

Definitely a good question that would require a little more homework and guideline digging to know for sure.

You realize that there is a lot you don't know yet and aren't sure how or who to trust.