Keller is getting pretty upscale and rents are going up.
I work for the City of Saginaw so I might be biased, but we have very good property values, great shopping and a very safe environment. The rents are around what you want for an average 3 bedroom home.
Watauga is where I grew up and values are slowly increasing but you should find something there.
Azle is out there- way west of everything.
Traffic is getting tough east of I-35W. The west side of the area is a lot better for traffic, but you end up going east anyway. Here in Saginaw you just don't live in the middle of it like Watauga. dad is still there and it's a pain to drive there through all the traffic.
Haltom City is another good choice. Good location, good shopping, etc.
North Richland Hills, Hurst, Euless and Bedford are all expensive to live in.
All the above have good access to the freeways to get to Dallas. Benbrook, Everman, Edgecliff, Mansfield are all out of the way.
Look hard at Saginaw, Haltom City, and the northern areas of Ft.Worth. There is developement going on everywhere in the north/west areas.
Let me know if I can help more.
Jim