You are very wise to get an estimate for remodeling before you buy a home. Many people dont do enough research before buying a fixer upper. Paying an expert to look at the home and give you ideas on what to change and the cost is the best way to go. You can try contacting architects to help with this. Some Contractors may be interested too..but many will not be interested because they are busy with construction projects. You can also try interior decorators and home inspectors..some of them may have the right skill sets. There are some online remodeling cost calculators that can give you a rough cost estimate like
http://www.remodelestimates.com