The only book you need to read to understand how to write an engaging sales letter (an ad with the intent to convert a customer) is read joseph sugarman's adweek copywriting handbook. Heres the link: https://www.amazon.com/Adweek-Copywriting-Handbook-Advertising-Copywriters/dp/0470051248/ref=mp_s_a_1_1
2nd thought. It's purely from a persuasion/copywriting perspective. I read this book a few years ago and one of the steps before writing is to imagine what opposition the reader could have before buying your product (or accepting your conclusion) and address it in the main text in descending order from most to least important.
For you I'd guess it's #1 establishing you are not a troll and not racist #2 establishing the facts that you proclaim are actually true
Here's how I support myself as a writer. Firstly, learn to write copy. I would recommend The Copywriter's Guide as it's a good starting place for those with a background in basic writing. Without much in the way of an advertising portfolio you won't get offers from agencies, but you can still work with small businesses and start ups.
At the entry level, Start-ups will be your bread and butter. Find a local entrepreneurial group and offer to write web or rewrite their current copy. Charge $20-$30 an hour. If you go lower, people won't respect your work. And always, ALWAYS know your price. Remember, taxes on freelance work is BIG. Always get half up-front, but be flexible. You'll also want to invest in someone to do your books.
Once you have a couple companies under your belt you'll have the beginning of a nice network. If you do a good job, they'll tell their friends, which leads to more work.
If you have any other questions let me know. Hope this helps and good luck!
P.S. If you want to make real money, become a medical copywriter. It's dry as toast, but I know a guy who charges $90 an hour and is always overloaded with work.
Yes, it's hard, but the most valuable thing I've ever learned. I took this course: http://kopywritingkourse.com/
My tips: take that course and read this: http://www.amazon.com/The-Adweek-Copywriting-Handbook-Advertising/dp/0470051248
Learn to write copy. Print money. But be ethical. Book