1) Way below market value, for example at least 20% below 2005 price, often find 30% below.
2) Then, verify county tax record, make sure it's also at least 20% tax assessment value.
3) Location: 70% or 80% good neighborhood, avoid top school district. Close to big hot metro regions.
4) 20-30% below median price of this region.
5) Have track records that can prove fast appreciation in the past for at least 2 decades.
6) Use high pressure psychological tactics to further low-ball the price, such as attaching a deposit check and etc.
7) Lastly, check market rental rate, make sure that cash flow is mostly even.

The problem with Dallas area is number 5) fails.