From a buy and hold perspective, if you're looking at an area with a lot of foreclosures that could be a red flag since it can be an indicator that the area is on the decline.

This is a huge red flag for most unless you have a good strategy for handling it. 

Most of the time if they pressure you to buy something on the spot, that is usually a red flag.  

Personally, this is a red flag.

That's a red flag on top of a red flag.  

Sales info is generally public or can be obtained from a Realtor or website.  6-7-8-9-10 times rent and now they are trading at 15 so maybe the market is overpriced or maybe knowing market players are anticipating strong rent growth.  

Anyone that says they deal directly with the bank is not telling the truth or, they are dealing with a one branch small player that doesn't plan on staying in business long.

As @Brian Burke says, might as well go to Vegas and bet on red:)

I have tried calling the back on some deals and it seems to be a lengthily process, of course because all the red tape we have to get through for the final action.

The last couple years there have been big players buying up all the good houses.