I don't see any need for networks (ever), but I am extra curious on why some people would say to not get one now and instead wait until you're bigger.
A network will not help promote your channel, assist in gaining more subscribers, or get you more views.
Instead, they'll likely have music available to use, a new dashboard for YouTube that shows a bit more information, and possibly be a level of protection to your Adsense account if there are any copyright issues.
If those few things aren't worth 10-30% of your income when you're making pennies, why would they be worth anything when you're making hundreds or thousands?
I would much rather pay a couple cents a month to try something out than to wait and pay tens or hundreds of dollars a month for the same exact experience.
Find a network without a lock-in agreement and test it for yourself...just realize that the experience you have with them would be exactly the same if you're getting 1,000 views a month or a million.
It isn't until a channel earns multiple millions of views a month where they start to assist, try for better ads and so on. Before then, a channel simply doesn't earn enough to be worth the time and effort required.