Hi!

Im making a total war style empire builder (turn-based, control cities on a map, move armies around) but need some input about "income". I use the full world map as the playing board, so it's a bit risk-like in that sense. There is 4 "resources" but I have mostly questions about "funds". Its modern day with some scifi elements. Most cities are destroyed but new empires emerges and rebuilds. The resources:

Power
Generated by power plants, some cities has better output from solar, biomass plant etc depending on world location (close to river: hydroplant is good etc).

Development / Research
Generated by population, but mostly from research centers/labs/academies

Fuel
Used for units. Generated by refinieries (efficiency based on local oil and gas natural resource). Or more expensively from synthetic fuel plants.

Funds
General and most important resource. Used for both buildings, infrastructure, spies and units. How can cities earn this resource? It's sort of "wealth". My idea so far:
Taxes
Mines
Agriculture
Logging? (might be used for biomass power plants instead)
Trade? (not sure if this fits the game)

How is "wealth" or general funds/resources generated in a modern setting, with totalitarian governments and full world war going on? Preferably something connected to buildings/infrastructure and/or the terrain/location in the world.

In a totalitarian global total war scenario there's presumably not much international trade going on, so something superlinear in the number of cities could simulate the value of non-local resources and specialization. If you wanted to get simulation heavy this could take into account resource diversity, but you could also hand-wave away and say "any city is going to be rich and poor in different resources." In essence by conquering a new city you got access to purer iron ore letting you smelt steel faster and produce more tanks, which is all abstracted into "more wealth." This would encourage snowballing for quicker games where somebody gets an edge and then conquers the world. Especially if you require geographic diversity this could have a counter where a player has to stretch themselves thin to maximize wealth, opening themselves up for counterattacks until they can resolidify with the additional wealth.

Another resource to consider is "stability": If people aren't being fed, they'll turn to scavenging rather than showing up for their shift at the factory. If people keep vanishing into the countryside to get away from missile strikes, specialized knowledge keeps getting lost. If the highways are crumbling, deliveries are slow. Here construction would lead to better stability (more farms, road repair projects, hospitals), but it would mostly be a function of not letting your cities be attacked. Spies sowing unrest, air strikes, raids on truck conveys between cities would do economic damage, so you could fight wars two ways: either seizing cities with troops for knockout blows, or wearing your opponent down and then going for the conquest.

Most countries have country-wide power grids, so to have an empire-wide power grid is a stretch, but not to wierd in my opinion. Not sure yet. Maybe powerplant could also just generate "funds" instead of being a resource of its own, or give bonus to factories (like in most civ games).

I was unclear:

I need several sources for income. Taxes (that affect happiness) and mining are a given. Maybe split mining up to give some more geographical significance?

But I want more:) Why is logging strange? Not modern enough? It seem a good choice to make cities still matter if not close to mineral sources. Wood is not used so much in infrastrcuture / military production though in the modern era...

I have "factories" for producing military units. But maybe have a choice between "mil factories" and "civ factories" like in HOI4. Civ factories would produce consumer goods, which yield income (funds). But this isnt so location-based.

True but let me phrase it like this:

What natural resources could suit? If i clump mining into one, agriculture into one. What else is there? Maybe this is enough but want to have all ideas on the table:)

I use oil already as "fuel". And forest resource is used for biomass energy. Maybe I covered everything? (i like rather broad cathegories of natural resources)

Also, you might be able to implement a "Scientific Funding" style of income. Say for instance, you have certain prominent(rich) people in your empire/cities, and they want you to research certain things and are willing to pay you to research them?