Where do characters in your campaigns live? It's sort of an unnecessary idea in a lot of campaign settings, because characters spend their days in dungeon complexes and by night end up in camps or village inns. But in Planescape, nearly every campaign has a base of operations in Sigil, and you can return to that base nightly after (and during) every adventure, because it's only a portal away.
1) Do characters in your campaigns have their own kips in Sigil?
2) How nice are those houses and where are they located?
3) If not, where do they live? Is it reasonable for someone to live in taverns?
4) How much do they spend on residence or do you just handwave rent, since domestic costs are nothing to the riches that an adventurer carries around in his pockets?
5) Speaking of portals, are there any in that house?
6) Do they all live together? Is it reasonable for all these characters to be roommates on top of everything else? Shouldn't they all have their own houses, since they presumably didn't always know each other? Isn't having the party split up for the night annoying and uselessly complicated?
I don't know where to draw the line between making it easier on the campaign and not spoiling those greedy little players.
1. In the games that I run and play yes, if the game is set in Sigil than players have a place for their kip, but that doesn't mean that it is a good place.
2. Starting off anywhere but the Lady's ward, unless there is reason to be in the Lady's ward. While land is expensive rental prices are within the means of an adventurer or party.
3. Certainly it is reasonable to live in a tavern. As long as there are rooms for rent and the party pays its bills. Just remember if they don't they could be out on the street with or without any possessions they left in the room.
4. If the party is doing well some loot should go to their housing, as landlords always call after you win the lotto. How much jink goes into it is more dependent on the players. Jink not only buys comfort it also buys security.
It also matters how well the party treats their landlord and residence. If the adventurers are just in for nights between quests causing a ruckus then the landlord will party with them, and present the bill promptly the next day(all damages included). If the party not only looks after their own but also makes sure to keep where their staying in order then the landlord probably would be more lenient.
Another notes is that in Sigil, even for high level parties, there will ALWAYS be a land lord. Land values are high in sigil in all but the very worst of the worst. The only "free" land is in the slags, and getting it is an adventure in and of itself. Around lvl 14 PCs may be strong enough to take solid control of a squat in the hive, by fixing it up and actually taking care of the place. By 18 they may be able to start thinking about bribing the right officials to get a legal deed to that squat. To truely buy land on the open market in Sigil you'd need a 20+ level bankroll.