I'm looking to buy a horse to put on the pattern I've found a nice ottb but he has a chip never been sore on it and the sales videos he looks sound on it and I was wanting to know if anyone has had success training a barrel horse with a chip he Is also 9 yrs old any advice helps

Not enough information. It depends on where the chip is. It also depends on if it's still attached or floating. Also depends on the size. If it's floating, I wouldn't touch the horse. At his age, surgery probably won't work. 

I have a good example for you. I went and looked at a 7 year old gelding off the track AQHA. He moves sound, but I noticed inflammation in his right knee, its was slight, but enough infusion when I palpated it. I then proceeded to flex his knee (hoof should flex to the elbow) and he was lacking range of motion. The owner said hes never had issues, and in the flexion test he trotted off sound. However, once I get that horse, put pressure on him, train him, he will become sore on it and I will have to pay for surgery (bone chip or bone spur) which I know from experience it cost $2500-3000, or I will have to inject... I WALKED AWAY!

Theres too many SOUND horses and I knew this wouldn't work for what I wanted. You're already questioning it... WALK AWAY. 

Can't always take their word for never been sore either. And they could be on bute or other drug in the video. I've purchased several from dishonest sellers in my time, but they've all worked out ok after spending a good chunk at vets & time for rehabs.  If you're really interested have a reputable vet, that is NOT their vet, come out and check the horse. Xray the area, do bloodwork, the whole 9 yards. Also ask their vet for all records for that horse, if the owner says no BIG RED FLAG. Don't ask the owner for the records they have, they can omit them. Ask the vet straight. Or walk away. I probably wouldn't buy one with a chip, even if they are sound now thats a big difference from being under the stress of training & competing. The stress of that will most likely make it an issue down the road if it's not one already 

RUN, do not walk, AWAY! There are way too many nice sound horses out there. I had an OTTB that had a chip that never bothered him... until it did... and his barrel racing career was over despite many many months and dollars trying to get him sound to run again tried every treatment out there and 2 surgeries later... he is now a happy pasture/ trail riding pet in his new home.