A quick google says a residential biohazard cleanup starts around $2500. Which I'd assume is for the smallest possible house, and this probably isn't a 1 bedroom if the adult son lives there. I'd be sympathetic if they asked for the money for supplies, a dumpster, etc. With that and all the elbow grease, they should be able to get it arguably liveable, if it doesn't need to be condemned. But expecting an outside company to wipe the slate clean for that amount is either delusion or a grift.