When it comes to any safety/crime related issues, it's always best to contact the local authorities with all your questions, hear all there is to hear firsthand. If unfamiliar with the area(s) do revisit more than once and at different times of day, possibly chat with locals/neighbors. Real estate professionals are prohibited from steering, enticing a buyer to purchase/rent, or not, in specific neighborhoods. http://www.neighborhoodscout.com/ https://www.crimereports.com/ http://www.homefair.com/
I would recommend you drive around Jefferson Park. Also, feel free to check out http://www.ChicagoPolice.org for crime stats. Work with a leasing agent to find you legitimate rentals. The ad you are referring to seems to be that, just an AD for leasing service, I don't believe that rental exists.