If you hire a company to repair your credit score there will be a cost, usually in the form of a monthly fee. This is because, like anything else, it is work, in fact it is quite a bit of highly skilled work that has to be performed over time. Just like any other job you hire a specialist to do, it will require an investment on your part.
For instance, you do not hire your friend next door to represent you in court (unless he is a highly qualified lawyer of course!) Further, when you hire a CPA, an attorney or even a plumber, those people can vary a lot in their expertise and experience. So, by hiring an experienced credit repair company, you are much more likely to get a positive result.