2-4 Plex in Chicago: Listings Vague on Number of Units

[Art Maydan]

I've just started looking for a 2-4 plex to buy in Chicago using FHA and a lot of the listings are vague on how many units the buildings have. For example:

https://www.redfin.com/IL/Chicago/1411-W-Grand-Ave...

Multi-Family (2-4 Unit), 4 Flat

Is it 2, 3, or 4 units? Also, what's the deal with illegal basements? A lot of these have some shady disclaimer about them.