So, how to make the action of sending out heroes fun, engaging, non boring, non tedious, etc, etc? I'm asking in a very broad sense (mechanics, UI, balance, etc).
There are a few games that do it. Majesty. My Life as a King. Recettear.
Most of us are quite familiar with the life of the hero. They go out on long adventures and save the world....
But those adventurers come back to a town over and over and over again. They sell all the stuff they bought, they go to the quest boards to look up new tasks. They pick up items, new potions, new weapons, new armor. They go to the various level-up buildings to gain new skills. They go to the big marketplaces for standard objects, and if the city is large enough they might also go to the black market, the thieves guild, pick up assassin jobs where the guards are on the lookout. Some cities focus on specific topics, a city of wizardry, a city of paladins and knights, a city of clerics, a city of thieves, a city of engineers and blacksmiths.
Knowing what the heros are doing as they travel the world, think about what the people in the city are doing. Then consider how the city's economy is built. What do they do with the piles of loot? How do they produce crafts for the arcane shop? How do they craft all that heavy armor, or the magically-enhanced armor.
With that in mind, you have some game directions. If you want to build a city focusing on something you'll need to create quests searching for items. Pay a premium for items that help your city, but doing so costs your city's treasury since you're subsidizing it. Get a profit for useless items since they can be mended or used as raw sources for the blacksmith or toolsmith or weaponsmith. If your town can get 500 gold profit for selling a flaming sword, posting a quest paying 200 gold for the missing flaming sword ingredients is a bargain.
Also consider levels of the party. If you are attracting high level adventurers they don't mind paying 500 gold for a stay at the inn, but novice adventurers are looking for a 4 gold bargain.
There are many ways to make that interesting. Maybe your townsfolk petition you for the ingredients they need and you use that to build quests to post. Maybe you balance the economy by building different buildings, figuring out how to use your limited space as an economy game.