This is somewhat difficult to answer. I guess the answer really depends on what tasks you are executing.
That said, the agent itself should have pretty low CPU utilization during most actions. Somewhere between 1-10% depending on how fast your CPUs are and what it's doing. You usually see higher utilizations on the actions the agent kicks off on the OS -- apart from what the agent does itself.
Basically it would be the equivalent of what it would take to locally execute similar commands. For example, if you're doing an audit, take into account what you're gathering (just a simple 'ls' vs. a full checksum on each file). Or in the case of a deploy, take into account utilization during a file copy / move. Like Sung said, it pretty much depends on what you're doing. But in the case of minor jobs, utilization should be pretty low.