I'm trying to find/make a report for my total income from all sources for the past 18 months. Some information suggests there is a menu item for Income Reports in the Reports menu, but I can't find it.
Under both the Standard and Classic menu views (set via the VIEW menu) there's a REPORTS menu. Look there.
[EDIT] I initially misunderstood the question. YES, Income and Expense reports are on the Spending sub-menu under reports. In Q, anytime there's a > to the right of a sub-menu, that means that there are sub-menu options. [/EDIT]
It is under the Spending reports, at Reports > Spending.
If you want to see the transaction details, use the Itemized Categories or Itemized Payees report. To see a summary by Category or Payee, use the corresponding Income and Expense reports. You can customize any of these to set the date range and select accounts and Categories to include by clicking on the gear at the top right of the report.