Well common sense would dictate that you would charge the client what it would cost you in materials, and your time to do the work.
That needs to cover:
1. Your time to do the work
2. Cabling (possibly different types, dependant on what you are actually doing)
3. wall boxes and ethernet points in the various locations, and conduit required for exposed runs.
4. Sundries (fixings, other bits you'll be using whilst performing the work)
5. Tool costs. You will obviously need normal installation hardware, plus the correct tools to terminate ethernet sockets and make plugs, as well as testing gear to ensure that they are wired correctly.
The fact its your first job, and you have no equipment might be a downer for you though in terms of costs.
Do you know what networking cable would be required, and how much you'd be needing to use?
What runs are you making?
Solid cable is preferred for runs where the cable is not subjected to movement (fixed point to point), and stranded for installations where flexibility is required (e.g. when connecting a computer or laptop/printer a ethernet faceplate fixed on the wall or in trunking.
You need to consider whether any runs would be subjected to strong interference. For these you would need shielded cabling.
Cat 5e cable is fine for most office environments.