Hi Mitchel,
I see Rick has already answered your question 
In addition to his answer I would like to ask: Why use Yolo through OpenCV? I would suggest installing Darknet directly and if you prefer working in python: the python wrapper.
So you can use Yolo without depending on a specific OpenCV version.
A more simple approach would be to use available pre-trained networks through a mature library like Keras. Which includes mobilenets which are optimized for low computational expense.
If you really want go the single shot multibox detection route, you could also look into Retinanet. Which has pretty clear steps for installation.
For an overview and comparison of modern neural net object detectors check out this article.
Regards,
Guus