There's a forum discussion o support and upkeep costs (1% of experience) and what it covers: Housing? Food? Equipment maintenance? Taxes? A mix of two or more? Everyone has a different approach. I think I want it to be part taxes, part housing, household supplies, and household servants. But I've come up with some rules for the latter.
The size of your household, in rooms, equals half your level, round down, max four rooms. At first level, you are sharing a room with someone in a boarding house or inn. You get one good meal a day included, and a storage chest with key. Higher levels mean a private room or small house, stocked with food,
You have one and a half household servants per room, round down. These are housekeepers, maids, and other lowly types. At 1st level (zero servants,) you don't have personal servants, but the head of the household has servants who clean your room, change bedding, and the like,
At higher levels, these costs include restocking supplies for the household, like wood for the fire, candles for lighting, a well-stocked larder, and so on. It doesn't include anything to take on an expedition. You can raid your household fo save a few bucks, but then there should be loyalty checks to see if the house staff reacts badly to you taking all the food and expecting them to make do with scraps, or taking all the candles and leaving them in the dark.
For now, I'm assuming half your upkeep costs is household, half is taxes. You can cut your costs in half and only pay your taxes, if you want to camp in the woods and scrounge for food, You can pay lower household costs based on a lower class level, which will get you a reaction penalty from some people (not living up to your status.) You can pay living expenses and try to skip the taxes, which runs the risk of legal trouble: 5+ on 1d6 (check weekly) means you escape the tax collector. Paying taxes at a lower level gives a +1 on the escape roll per two levels: if you are 6th level and pay taxes as if you were 4th level, for example, you get a +2 on the roll, which gives you a 2 in 6 chance of escaping the tax collector. (Yes, this means that a Lord who hasn't built a stronghold yet and pays taxes as if he were only 8th level gets away scot free, while a 2nd level fighter who pays half his taxes has a 4 in 6 chance of getting caught. The rich are lucky jerks like that.)