"So does that mean I don’t need to file a DC state return even I have the rental income in DC?"
That's correct. DC full year non-residents are not required to file a DC income tax return, DC Form D-40. (Business taxes are a separate issue.) But your rental income is fully taxable by your home state of Illinois and must be reported on your Illinois income tax return..
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
