We have found a beautiful house built in 1951. the builder was a wealthy doctor, He spared no expense in materials and used asbestos for the roof shingles, also on the pipes in the crawl space and possibly in the walls. Should this be a health concern for my family? also the roof is approx. 2800 sq.ft. and the asbestos/cement shingles are 48 yrs. old there are no apparent leaks. but if they develop, will it be expensive to replace?