How to convert photo to a vector drawing
This problem is known as "style transfer", and deep learning can achieve some pretty amazing results.



Here's a fantastic GitHub repo with an easy-to-use implementation of neural style transfer (usage instructions).  I think you'll have better luck using a pre-built model like this rather than training your own.

If you want to train your own, this repo might be a good starting point.  It has a training script included, you'll just need a bunch of training images and a style image.