Start with your local library. Mine lends tens of thousands of ebooks. It also has partnerships with other local libraries in the region that allow me to borrow from their collections as well.

I don’t think there is such a thing as inter-library loans for ebooks but you should be able to borrow from pretty much any library in the country if you are willing to wait for a paper copy to be shipped to your local branch. There may or may not be a fee associated with this but my local library allows me ten ILL requests a year for free.

Libraries are such an underrated and underutilized resource.