Any ideas for what to look for in a property management shop that would even take me?

I invest in older homes, short answer is yes, I think it's a good idea and I've added that to my list of due diligence.  

Any idea on what interest rates would be on that? 

If you're an experienced real estate investor living in or around Springfield, IL, I'm looking for someone to provide advice and constructive criticism of my ideas, plans, research, and goals with.

Great idea of expanding!!

Run your business like a business.

I've included a preliminary floorplan below.My goal with this ADU is flexibility in terms of renting it out either short-, medium- or long-term rental in the future for income, as well as maximizing resale value (main property is 1300 sq ft 3/2) to someone probably with an investor mindset who would want to house hack.My main concern is whether it's a good idea to have 3 en-suites at the expense of having a small living room/kitchen area.

In majority of instances seller financing for the seller is a horrible idea and should only be an option when the home doesn’t get conventional financingMany will disagree with above which is fine - it’s similar to winning lottery and taking lump sum over payments.

Does this person have a business license?

Make sure you confirm the value of the property, the business income and expenses, and confirm the borrower’s experience.