Table income and expense is better to have it together or apart
If you consider income as a negative expense, and have categorised it sufficiently, a single table is just fine. The columns describing an income transaction are essentially identical to the columns describing an expense.

You can easily have indexes that allow you to quickly find your income or expenses, based on your categories (because negative income is not necessarily an expense, you should have things categorised appropriately). And with an index on time you can easily pull up your change over time.

If you're doing double-entry accounting, you should be able to easily add up your transactions and see they always add to zero. It's a useful test for consistency. Then some reports will leave out "equity" lines to compare Profit and Loss, etc.

If you use separate tables, you can use UNION ALL queries to query across the lot, but I would consider this extra effort you don't really need.