Last month I had a similar plan to look for an ID who only helps me design and manage the renovation project. Therefore I asked my contractor to recommend a good interior designer. The ID called me and asked me to email her the floor plans. Three days later I got an email from her and she quoted $7,000 for design & site supervision fees ( 80% upon comfirmation & 20% upon delivery of job ) without providing any design plan or proposal. She did not mention anything about my floor plans. I doubt she saw the floor plans or not. How could we trust such 'good ID'?
Some ID companies charge $1,000 for drafting 3 3D drawings.