What's the best way to test if I can withdraw the royalties from Amazon KDP?

I came up with a lot of book ideas and checked demand for them. Each separate book is going to take months of writing to be publish-ready.

However, I haven't made any money online before and I had to use Payoneer as my payment method on my Amazon KDP account.

I need to publish something this week that is guaranteed to sell enough copies for the minimum withdraw threshold so I can test if I can actually get paid.

How to find genuine yet short topics to write about?