Making money from Kindle , updated guides?

Hello

does anyone know or can link a good updated (2018) guide on how to make income by ghostwriting Kindles? It looks like Amazon has changed its policy a few times in the last 12 months. also most of the guides around online cost between £500 and £1000 which I unfortunately can't afford

so far I invested quite a lot of money and time into Kindle with very little return.

Thanks

I'm interested as well

The blog Kindlepreneur has tons of free resources and updated info.