Domain flipping or Selling Advice

Hi,

I am about to try making some money with selling domains ... But confused ???!!!

1. Is it worth in 2018 ?!
2. What TLDs are best sold after .COM ?!
3. A .PW domain sounds cheap and can make it short LLL or so domain name, but is it any good ?!
4. I need free resources and tools to use so what you suggest ?!
5. As a starter where should I sell ?!
6. Any help or suggestion is welcomed ... !

NJOY :)