It depends on your platform. It depends on what you have running on your server. Do you have 8 databases running on it or one? Do you configure your agent to collect every single possible metric as often as possible or do you disable all your metrics....or just some?
The question is impossible to answer.
Here's an idea, instead of listening to someone who think it will take up a lot of resources, why don't you install the agent on a test server?
Groundbreaking ideas don't come better than that... ;-)