It's hard to say when you don't give any information about your channel.
Here are a few items that I would make sure to discuss with any network.
1. Will I still have access to my YouTube Analytics/Estimated Earnings information? If the answer is no, then I would not even consider that network under any condition. Make sure that your access to that information is in the contract.
2. Length of term. 1 year? 2 years? How much notice do they need if you want to leave?
3. Are they only an ad serving network or do they look for other monetization opportunities? Product placement, channel sponsorship, etc.
4. What is the agreed split? 70/30? 80/20? Are there any other hidden fees or charges?