Sales History Concern

[Justin Chambers]

While browsing for properties I have run across a few houses that seem like they may be a deal. After further investigation the properties were bought maybe 3-6 months prior for half of the current list price. I've seen this a few times and I'm just wondering what gives? Are the sales histories on MLS websites not reliable? Are investors picking up properties for cheap and immediately turning it around for a profit without any rehab? Did an investor buy and find a major fault? All the properties I've seen like this are still in need of rehab to be rent ready. I'm a newbie so maybe it's a dumb question but any insight would be great.

Thanks!