This is a good post, I think a lot of people are under this assumption that you described when starting out, like myself. We bought a property that looked great on the spreadsheet, 10-12% projected returns. But out of the 2.5 years we held this property, we had positive cash flow in about 3 months of that time. We were focused on the numbers and we ignored the area we purchased in. We happened to unkowingly purchase a property where there was high level of gang activity. This drove away good tenants and only attracted headaches for the entirety of our ownership.
We were lucky enough to have been able to sell this property for more than we purchased it for, enough to mostly cover the losses we had endured, though I'm sure there are other who weren't as fortunate. We lost some money after all was said and done, we considered this our cheap education and will be moving forward with much more dilligence. I hope those starting out can take from your post and avoid some potential headaches.