You can get 'As-Builts' made, we did this recently in preparation for some remodel work - often people looking to break into home design will look to do them. I would check with home designers in your area and see if they have anyone they recommend.
Also check with your city - blueprints are on file going quite far back in many places.
Also check with your city - blueprints are on file going quite far back in many places.