It's obviously your house IRL.
Drive along the street until you see it, duh.
(No, it's my old house, I don't live on the East Coast. Many memories in that house.)
You knock on the door, and a man with a scruffy beard answers. "Wow, you don't look like I expected." he says. "You'll need to fit in with the NCO look." (hint hint? new inawoods-using char coming up along with something eeeelse) "Look, you came here for the GSOS. We're not the GSOS. We're the NCO's base in the GSOS territory. We had to put it on such a secluded street because otherwise the GSOS - which has a close outpost in Boone Park, where the old tennis courts the famed Bill Ivano played at, and they've got their main HQ in the old Prime Osborne Center downtown. Their main operations base for work regarding attacking us is actually in the old LaVilla Arts School downtown, near the Osborne center."
"We don't want you to mess with the HQ, we want you to mess with the old Art's school. There's a bedroom where one of the prime figures is supposedly sleeping. Room 210. Fittingly, I went to that school, and that teacher was a b-i-t-c-h bitch. So go in there, and kill the figure. he's wearing a green blazer and has glasses on, with jeans. We don't know much other than that. Go kill him."