People with high risk behavior sometimes do have both. In the absence of high risk behavior, it is still possible to have both, but vary rare. Both diseases are spread by blood to blood contact; HBV is spread by sexual contact as well. HCV is rarely spread by sexual contact.
There are many variables, so telling you what you can expect is close to impossible. Do you know if you have an active Hep B virus or did you once have it and now have antibodies from that previous exposure?
You should see a hepatoligist as soon as you can. You can usually find one at a major medical center. What part of the world are you from? There are people here from all over and you might be able to get a recommendation from someone.
Good luck to you.
Did you also post this on the Hep B forum?
I don't know how common this is, but drs always warn us to get tested and vaccinated for Hep B when we're diagnosed with Hep C.
Actually, I just googled coinfection of hep b and c and got a good lead from a dr on medscape.
He says it's not uncommon, but complicates treatment.
Good luck.
Bug