Use the pcxtodxf or pcxslt18 program in the "rc/software" directory to convert 
the scanned plans from the PCX, Paintbrush, format to the DXF format.

OR 

From: dolanosa@interaccess.com (Butch)
- Copy from article in rec.models.rc,"Plans to DXF converter...EASY"

Scan the image (as clean as you can get it) andd save it as a TIF file.
Use a friend's Corel Draw (4.0) or your own and import to CorelTrace.
Trace the file so that it is exported as an EPS file.
Use CorelDraw to import the CorelTrace EPS file and save as a DXF.  This will 
make sure that you will get all the lines and text.  

Hope This helps

Butch

P.S. another thing that you can do is to scan the image and have a drafting 
company vectorize it for you.  Make sure that your scan is of good quality.

Butch