ISIS gets funds by shipping oil to Turkey "Russian fighter jets smash ISIS oil tankers after spotting 12,000 at Turkish border" http://www.express.co.uk/news/world/629409/Russian-jets-smas...

Where it's quite likely traded by Erdogan's son http://www.mintpressnews.com/211624-2/211624/

Various on Quora https://www.quora.com/Is-Turkey-supporting-ISIS-If-so-why

ISIS fighter having a Turkish beach hol before getting back to the beheading http://www.dailymail.co.uk/news/article-3173135/Jihadi-swimm...

I think Turkey is a similar situation to the US supporting Bin Laden and the Mujahideen in Afghanistan to try to get rid of the Russian proxy except in Syria this time.