Upkeep is already priced into the wealth by level guidelines, and this is part of the reason for discrepancies between those guidelines and a straight extrapolation from random treasure tables.
From Dungeon Master’s Guide pg. 54:
BEHIND THE CURTAIN: TREASURE VALUES
There’s a relationship between Table 5–1: Character Wealth Level,
Table 3–5: Treasure, and Table 3–2: Encounter Difficulty. Writing
adventures following the guidelines in this chapter, and using Table
3–2: Encounter Difficulty, should generate enough treasure using
Table 3–5: Treasure to keep characters abreast of the wealth figures
described in Table 5–1. In fact, such adventures should provide more
wealth, because characters expend some money on scrolls, potions,
ammunition, and food, all of which get used up in the course of
As you can see, rewards using these tables generate more wealth
than indicated. We assume characters use up that additional money
on expenses such as being raised from the dead, potions, scrolls,
ammunition, food, and so forth.
Your job is to compare the wealth gained from the encounters in
your adventure with the expected wealth gain shown on the table
above. If your adventure has more treasure, reduce it. If your adventure has less treasure, plant enough treasure not related to encounters to match the value (see Other Treasure, below).
Your job is also to make sure that wealth gets evenly distributed.
The third column in the table above shows that each character
should get an equal share of the treasure from an adventure. If a
single item, such as a magic staff, makes up most of the treasure,
then most of the party earns nothing for their hard work. While you
can make it up to them in later adventures, it is best to use the
methods described in this chapter to ensure an even distribution of
As such, if characters are kept roughly to the wealth by level guidelines, then it can be assumed that they are paying for their own upkeep. The numbers are designed such that you don’t need to track incidental costs associated with upkeep.
Put another way, the wealth by level guidelines are specifically wealth—they represent how much value a character’s useful, valuable equipment and gear should be worth to that character. It can and should fluctuate quite a bit around the listed value, of course, but it should generally be the target, and if you’re on target, things are going well (at least, according to the Dungeon Master’s Guide).
The Dungeon Master’s Guide does list an optional upkeep rule on page 130, but this is really only if you want more emphasis in your game on the subject of upkeep. Since you are explicitly looking to limit the need to track these things, I recommend simply using the wealth by level guidelines. Things like lodging and meals can be ignored unless you want to roleplay a particular night or meal, and even then the costs can be abstracted—or even waived in-character, as a form of non-monetary reward.