It's a glutted market and so that drives down the rates. Although there are plenty of ladies that do charge upwards of $500, that is the TRUE exception and not the norm.
If you look on backpage, or other like publications, you'll find rates at $120 for the hour upwards to the average of about $180-300, which $300 being the higher end of things.
I don't like the rates going down, but I'm attempting to give you an accurate idea of what's going on in Dallas.
The climate is fairly cut throat, if you're on the local boards because of the competition, although we don't speak of it.

Although it's not as "hot" as some areas, there are areas in DFW, like Arlington, to avoid. You can find out those areas pretty easily by just asking around like you are now.
I would say that most appointments are incall. I've had a few friends who have thrived doing ONLY outcalls but it's the exception, again, and not the norm.
Good luck. For a new person, or an agency, I would think that working in DFW would be a challenge unless you can become the "Flavor of the Month" or if your gorgeous (I haven't looks at your profile, sorry!) ... and very slim, you will do just fine.
If you're middled aged, more average, and more on the frumpy side, I wouldn't suggest giving DFW a try.
Just my thoughts. Good luck!