Tracking cost of living is usually best reserved for months or years of downtime since that's when someone might earn a substantial amount of money from downtime activities and find that costs really add up. You can usually ignore it if there are only a few days of downtime, though if a PC is roleplaying a fine or extravagant lifestyle, you might charge them during even short periods of downtime to reinforce the story they're telling. For short periods of downtime, characters are usually just passing through a settlement or spending a bit of time there. You can use the weekly cost of living listed in the Cost of Living table and divide by 7 to determine the combined prices of hotel rooms and meals per day. Deduct these costs from a character's funds after they gain any credits from their other downtime activities.
A character can live off the land instead, but each day they do, they typically use the
Subsist activity to the exclusion of any other downtime activity.