Solo Campaign Mode - More than one instance at a time

My son is playing Reach solo campaign mode, and I want to start my own solo campaign mode. Is this even possible? And if I do eventually start a new solo campaign, will I wipe out any previous saved game that is on there? If not this sucks because I am not going to buy another xbox and reach game just so I get a chance to play…

Thanks

Just make an extra gamer profile on the xbox itself and keep the profiles separate - one for you and one for your son!

Thanks, did not know that was possible, thought it was a one ID setup.