Multiple GPUs one expensive GPU, which gpu to buy for real time processing (not training) I am trying to decide what GPU or GPUs to buy to run tf-pose pose detection and yolo3 object detection on several cameras. I need to keep an acceptable frame rate too. 

what kind of GPU configuration should I go for?

does having multiple GPUs have an effect on what I am trying to do.

can you please explain the difference between using 2-4 1080ti(any GPU in that price range) cards and using something 10 times more expensive than that such as v100.in training and using the networks both
Here's a link to some benchmarks that should give you some insights.

In my experience (I've used systems with both 1080s and V100s) I've found that as of about a year ago, a lot of the common tools couldn't use the V100s well.  Until we started doing some manual optimization, the 1080s were comparable if not better on common tasks.  Of course, once we put in the time to optimize, recompile drivers, etc., the V100's really came to life and outperformed everything else by several times.