"How do I write emails that will bring client results so that they can keep paying me?"
That's one of the questions I usually hear from beginner copywriters. See to be good at copywriting you must learn from the best.
It's a common phrase that "The best copy isn't hidden" so I know a free place which you can study copy from any niche.
It's....(Drum roll) bradadadadada, FACEBOOK ADS!!
After studying them from about 8months I realised that facebook ads are alot like email and if you study them you'll see the pattern of how good copywriting looks like.