It pays to be picky about the building. Find value where others dont, then you'll get a A+ building for a (hopefully) B- price.
Easiest indicator of this is when you see tenants that seem "out of place". If you find tenants that seem like they're better than the building or rent determines, then it might be a good deal. For example if the building is full of engineers, corporate frat boys, scientists, marketing people..etc white collar, 60-100k+ jobs but the rents are 800-1000 , then the previous landlord was probably behind the times.
Three real life examples:
1) Purchased in 2011 for 180k I've done almost no repair work on it (besides painting the exterior and general main), I'm grossing around 3900/mo from it, my expenses are around 1200. Circa 1907 building, 3 units. Floors are def a bit wonky, two octopus furnaces, two staircases to no where.
2) Purchased 2016 for 600k, I've spent about 100k remodeling the building, adding bedrooms (added 4 total throughout the building), remodeled bath/kitchen (granite, stainless steel, backsplash, tile..etc), rents were ~5000 in 2016 and now they're 9-9.5k. Based on rents building is worth somewhere in the range of 950k-1.05. Similiarvintage at 1913, floors are wonky but stable.
3) Purchased 2018 for 562k, triplex, was empty when I got it, now it's doing around 5700-6300/mo, it was actually moved to the site in 1911 as a house, split into 2, then the attic converted to 3 (got all of the permit history for a different reason). Floors are really wonky, but due to that, the condition, and a few other things I got it for 562k, where as a unit across the street sold for 700k last month, and I'm going to convert mine into a 4plex. Hoping for a value around 1-1.1 as a four, with a cost around 200k including remodeling the existing units.
Look for these things in any property (or the ablity to get the building to that condition easily):
1) Young trendy tenants with A+ jobs (tend to pay rediculous amounts of money in rent)
2) Under-rented currently (landlord is behind the times on rent)
3) Undervalued currently (because people dont like slanted floors for example)
4) Good and IMPROVING area, not good but declining
5) Most important I've found in leveling up is the ability to add value. Find value where others cant see it, add bedrooms or units, remodel stuff, get more money from the stuff you already own, ring every last cent out of it, including con op laundry. The more value you get out of each building also means that each building is worth more if you wanted to sell it. Take a building that's worth 500k making 5k a month into a 800k building doing 8k a month (simplified numbers for the example).