We sometimes have a sense of labor’s value, but with potential new jobs that exist in SF or fantasy, we may need to be creative. Being plausible is once again our goal. Local conditions will impact this and we can invent that on the fly. Maybe I’ll earn a meal by chopping wood for two hours in one place, but it takes four hours in another. Why would this difference occur? The longer time means by labor has less value there. This might happen if there are plenty of potential wood choppers around. Conversely, if this is rare, maybe I’ll get by with suggesting only one hour.
Chopping wood isn’t unusual labor, but think of some unique jobs that might exist in a fantasy setting, given the plants, animals, and existence of magic. What if a wizard needs someone to practice casting a spell on? We’d imagine this quite lucrative, given the risks. Perhaps they need someone to assist as they prepare a potion or summon a demon.
In SF, gadgets and phenomena similarly offer opportunities. Maybe we need to test a device, whether that’s dangerous or not. Cleaning radiative sludge somewhere might be needed. Imagine anything dangerous or just unpleasant, depending on how much risk we feel is needed. It’s great when the experience changes our character or plot rather than being an aside, such as radiation sickness impacting a character’s ability to perform like usual days later when they need to.
In both genres, there could be an animal that must be fed, or watched even though it’s in a cage. Plants might need sowing, harvesting, or preparing, which doesn’t sound interesting unless there’s something special about this. Examples would be harvesting a man-eating plant, or cooking one which produces lethal fumes if not prepared right. Get creative when characters have no money and need something.
If they want to earn money rather than food, lodging, or transportation, we assign a value based on rarity, danger, or story impact. For example, if chopping wood will take two hours, which they have, this doesn’t impact the tale (unless they hurt themselves). But if they don’t have two hours to spare, this poses a problem. We can therefore choose a task and assign a value that will negatively impact them to a degree that seems appropriate to us. It can also have a positive impact. If chopping wood for a set period of time would earn me two silver pieces and I only need one, I could bargain to reduce the time or just take the extra money.