Misunderst0_od:
I think he was mostly interested in the property because General Meng is the one who recommended it (for the location) rather than the "kind souls" with unknown intentions. It might have just been pure coincidence and luck that they stumbled upon this case and struck a blow to the Crown Prince (super convenient). Maybe the novel has more answers. o_o??
To close the loop on the house where the bodies were discovered, from his conversation with Tong Lu (the vegetable seller who is passing messages for him) he did not stumble accidentally on the brothel case. From the conversation wtih Tong Lu (~ep 10) it can be inferred that Tong Lu's sister was one of the courtesans that was murdered in the brothel and dumped into the well. So he wasn't lucky it was planned.