Masonry

we have a problem with water in the wall of the unattached side of our brownstone. We had a home inspector come by and he said it was most likely a crack in the side wall, or it could be the roof, or perhaps the back wall needed re-pointing. He then described standing and hosing the wall for about an hour to see if there were “results”. Am not quite sure what that means in terms of the rapidity of seeing results. Would that be immediate, or would it be several days? Also, I assume we should remove the crumbling and staining before doing this so that we can see something new. Is there a company that would do this for us? The thought of dangling over the edge of a four storey brownstone with a hose for an hour is not terribly appealing. Also, does anyone have a mason that they would reccommend for this type of work? What about the mold that is already present? Does that need special work, or will the mending of the leak fix everything?