In a city with no prominent industry, people will always needs healthcare, childcare, food, and maintenance on their belongings.

Healthcare: doctor, nurse practitioner, nurse, dentist, dental hygienist. Skin and hair care might be stretching the category, but everyone needs haircuts.

Childcare: teacher, ECE, nanny. Big spectrum here from no training required to professionally registered.

Food: production, supply, distribution, and sales. So farmer (but that's capital intensive), food maker (baker, chef, cook, butcher) or distributor or seller.

Maintenance: vehicles (tires, oil changes, body shop, parts, detailing), homes (carpenter, painter, gas tech, electrician, window installer, roofer, landscaper), appliances (appliance technician), power equipment (mechanic, blade sharpening).

Probably more, but that should be a pretty decent list to start with, and all should be pretty portable no matter where you go, save for certain licenses that may be specific to a state or province.