All an MCN does is take a percentage of your revenue in exchange for.. Well, pretty much nothing. Nothing you can't do on your own. The only advantage they provide is giving you more "protection" in a sense, if you're a big YouTuber with over a million subs. If you bring in the revenue, they'll treat you like a valued part of the network and help you get verified and protected from unreasonable copyright claims. If you were to join multiple networks, bye bye revenue. YouTube takes 45% of your revenue already, leaving you with 55%. And then a network would take a percentage of that 55%. Add in lots of networks, and you'll probably end up with only 5% or less of your revenue. Would not recommend.