If you hire a credit repair agency to help you repair and rebuild your bad credit then it costs from $100.00 per month plus they'll usually be a one time fee of around $15.00 to access your credit reports.
Be aware that hiring a credit repair agency won't repair your credit right away and it can take up to a year to see your credit improved so it can be costly.
You should pay off any debt you owe which can help you repair your credit rating and take out a secured credit card and that too will also help to rebuild a poor credit rating.