I grew up in “very rural Midwest, USA”. My hometown’s population is less than 5,000, and it’s the biggest town in the county. Some other have already covered the “invisible” jobs that are everywhere, but here are some more examples. If there are houses, there are realtors, builders, inspectors, insurers, landscapers, and service techs (think plumbers, electricians, etc.). Aside from the people you see working in stores, schools, hospitals/doctors’ offices, etc., there are the people you don’t see most of the time like cleaners and maintenance people. Even the tiniest little “town” usually has at least a gas station and/or bar, even though sometimes they’re the same place. There are also police officers, sheriffs, lawyers, judges, and other city/county officials.

Someone mentioned truckers, and even though my hometown was nowhere near any sort of metropolitan center, some independent OTR truckers lived there. And speaking of transportation, cars/trucks are obviously important in rural areas, so you’ve got new and used car dealerships, mechanics, tow truck drivers, etc.