In addition to the sources Tom mentioned, you might see if AI generated options would work. That clearly isn't a good option if you're creating a tour of a real environment (you need a real 360 camera for that), but to just make up a generic office or something it might work.
I attended a webinar yesterday by Garima Gupta, and she shared the Blockade Labs Skybox as a tool for creating free AI generated 360 images. They have some AI weirdness, of course, but it might be worth experimenting with (especially up to your limit of free images).