When I first watched DGSD '81, I was, for some reason, under the impression that Tsui Yin Manor was Dr. Sit's home. Only later did I realize that it was the home of the Yau family.
Tsui Yin Manor was quite a large estate, capable of hosting a Heroes Conference attended by hundreds of wulin warriors. It takes quite a bigwig to have a property like that in wulin. The Yau Brothers' martial arts weren't that great (or maybe Kiu Fung just made them look bad, the way he does to almost everybody who fights him). Were the Yau Brothers really such wulin bigwigs that they could lord over a property such as Tsui Yin Manor?