Why would you hire an attorney to clear up your credit score? Same as hiring a dentist to do your taxes, or hiring a pharamcist to represent you in court. All those professions require knowledge and training, but stay within their strengths. An attorney won't be much help to you in cleaning up your credit.
Next, there's no 100% financing (from traditional lenders) anymore. You could have an 800 credit score, and you wouldn't get 100% financing.
Next, you're talking about buying a commercial property. (You could finance four units as a residential property, but most lenders won't.) And the rules of the game are quite different for commercial properties. Your lawyer/credit expert should have told you that.
Best bet: Look for seller financing. Find someone who owns a quadraplex and wants to sell. Have him/her take back financing. But be sure to do your due dilligence on the property first.
Hope that helps.