Find one agent you trust and take that persons advice.
I have seen that modification on same model done before on home located on Fairlawn. Realize that the home you ask about is already a quad level, it's a tri-level with a sub basement and the addition you are thinking of adding adds another staircase. The house i was in that did the expansion up was very choppy floorplan. If you want bigger, you can get a regular 2 story Libertyville 4BR colonial under $450k and not need to do the work, and ultimately harder to eventually sell. Plus that house on Hayes is 3BR up and one in the lower basement level. The house you are asking about is asking 369k, you get alot of house in Lib for 350-400-450k and avoid the headaches of major expansion.
If you are not working with another agent, I am happy to set up a custom MLS web link. Call, text or email me if I can be of service.
Thank you and Best Regards,
2009 & 2011 Chicago Contractor of the Year, Angie's List
2008-2011 Super Service Award, Angie's List
RER/MAX Suburban Libertyville