Can you share a bit more about your strategy? If you're just looking for multifamily near a train on the northside for under $400k, Redfin is a great place to start. But if you're looking to partner with someone who knows what their doing, you might want to have a little more info than that.
From what I am hearing, there are no more cash flowing multi-families on the northside (especially close to a train) for under $400k that are not being gobbled up in serious multiple offer scenarios within days of going on the market. People being outbid by several tens of thousands. In fact last year I was outbid on a 3-flat by $70k and I was offered $17k over asking (List $329k, I offered $346k, it sold for 418k). The sweet spot in Chicago multi-family last year was $400-500k. Everything less needed too much work and everything more was too expensive to cash-flow (at least until you got to the $700's). This summer it's gone nowhere but up.