IP geolocation is not very reliable. I deal with that kind of junk all the time for work.A very handy tool on TX Gun Trader is the IP address location feature.
When you open an ad look just under the sellers name. There will be a little red crosshair looking icon.
Click on it. It will open up another page with the location of the ad owner IP address.
Match that with any location in the actual ad.
If the IP is shown as outside of Texas its a scam. Hell I see them on there from Lagos, Nigeria frequently.
Many of the scammers somehow list Dallas so be careful.
If the ad says For Sale in Houston and the IP locater says Kansas then you have a fraud.
Only do live face to face deals. Never ever agree to shipping/sending money.
Contact the seller thru the Trader website.
Edit: BenEnglish already said about the same. It's hard to get scammed if you meet FTF.