apostrophe question (subjects' or subject's) neighborhood

Is there one subject, are are there multiple subjects?

only (1) subject . . . . the phrase is used within the real estate community . . . . referring to a particular house ( 123 Main Street ) . . . . " In the subjects' neighborhood there is a pool and tennis court."

If there is one subject, then it's subject's.

If there are multiple subjects, then it's subjects'.

Is that really typical language? Referring to the homeowner as "the subject"?

thanks for the help!

more specifically it's used in a real estate appraisal report, with mortgage brokers as the intended user . . . . instead of repeating the house address throughout the report, the address is "abbreviated" / referred to as "the subject property"

Great answer thank you for the clarification I always mess it Up!!

Yes, when referring to the property or the dwelling in real estate it is typically called the subject.

Neighborhood's pool or neighborhoods' pool