Before you have access to dig yield, your primary source of income will be contracts.
Terminate any contracts that are not quick or easy. For example, preventing power outages for 10 minutes is not quick, but it's easy so I'll do that one. Increasing shelter coverage is a great one because, before you hit that 1 star mark, you don't need any shelters because there's no storms, so just demolish it after completing the contract and you'll make a profit (but don't forget to build one once you reach 1 star!) Same thing applies to build fast food, gift shop, etc, because you can just demolish it after you complete the contract to make a profit.
Some contracts are terrible but expensive to terminate (such as "allow X to kill Y in combat) but even then it's still better to terminate it in favor of hopefully getting a better one.