From a value/resale standpoint, converting a 2-4 flat into a single family house, in many neighborhoods in the city, possibly Albany Park, makes little economic sense. The cost/benefit analysis probably does not work, but if you really really like the building/area and plan to stay for a very long time.......perhaps.
In theory, you need to get permits to redesign the place so you need an architect/licensed contractor, but depending on the amount of work involved, you might get away with doing it on your own. Based on the questions you are asking, I think you probably should get some help and crunch the numbers before you do too much. Did you already buy something or are you just looking???