As O'Keefe said, this is a group-by-group thing and you should go by what feels right for you and your group as for me, here is my philosophy when GMing:
- You can earn all kinds of things through roleplaying without paying for them with money or experience, but to do that you really have to earn them. If you are paying for them with money and experience then a reasonable in game reason is enough.
The way this would apply to the situation at hand is that if he fully plays out the whole hunt the werewolf thing with you, takes all the risks that entails, and succeeds then he gets all the rewards of that. He gets experience from it, he might get reputation, he might get spoils of war if the werewolf had something interesting or valuable.
But he does not get several dots in lair. He hasn't earned several dots in lair. He has earned one dot in lair, if he wants it, for now squatting in a very large, very insecure compound. This compound has been furnished and secured for that werewolf, not him. If it had traps, he probably either destroyed them on his way in, or may still not know about them so they are still dangerous to him. If it has locks, he might not have the keys, same with any combinations. Secret passages are likely still secret to him. He may have broken down some of the doors himself and possibly damaged the structure in the fight. If it had alarms or a recording system, he may not have the codes or controls so they may not do any good for him. In fact, they might actively cause him problems until removed and replaced.
Worse, part of the security might have been the werewolf's reputation itself. Now that werewolf is gone. The werewolf's heirs might be coming looking to inherit their father's/mate's/brother's lair. The werewolf's rivals might be coming to steal it for themselves or at least loot it. On
On the mundane side, if this is private land, there is a legal owner out there somewhere that might be sending the sheriff. (For that matter, if the werewolf maintained a legal, human identity then the character just comitted murder and he is considering living at the scene of the crime....) The county wants the property taxes. If this is public land the warden/ranger might not even notice a werewolf living there, but won't take kindly to a human squatting there long term.
Once he has dealt with all of that, then he has earned several dots in lair.
I would give him a choice: He can either spend XP and cash to represent dealing with all that and buy the rest of the dots that lair is worth (after he got the first one for killing the werewolf). Or he can earn them through roleplaying, over time, by repairing the damage, gaining control over the security measures, dealing with the supernatural forces trying to take the lair from him, and dealing with the government entities (whether that means working through bureaucracy and gaining title or bribing some officials and staying concealed from others is up to him...)