I wonder though, ignoring everything else... the site itself?
Who'd want to live in the same space where 70 people (likely) died (horrifically)? It should probably just be turned into a memorial park with a stone engraved with names.
Without wishing to be callous, it wouldn't phase me in the slightest. If, for example, a house had been the site of a grisly murder that was consequently on the market for cheap, that would actually be a plus to me due to the saving. (So long as it wasn't "in the nationals" grisly and I was beset by tourists or some such).