The first kind is the ones that Apple wants - they are the likes of Comcast/Optimum/etc. There are the ISPs that have lots of eyeballs and have captive audience. If Apple has shitty connectivity to them, it is going to be bad for Apple ( because consumer cannot replace such ISP - there's no real competition in those markets ). These are also ISPs that happen to peg their transit PNIs or free peering PNIs as much as possible forcing others to to buy paid peering to have non-shitty connectivity to them. These ISPs are going to charge Apple for colo, power and bandwidth and Apple is going to pay and it is going to pay through the nose ( just like Netflix does and just like Akamai does )

The other set of ISPs are the ones that want Apple a lot more than Apple wants them. There's no way Apple will pay for access to their customers. Those ISPs are going to give Apple space, power and even bandwidth for free. Hell, they may even have to pay Apple.

Source: did that for both ISP side and content provider side (at different times)