What are your options -- what have you looked at?
A really cheap book is
The Ultimate Sales Letter by Dan S. Kennedy. You can grab a copy from Amazon for just a couple of dollars. It's an author, if you don't already know, that ALL the great marketers rave about, and have a number of his publications in their back pocket at all times
With that said, I haven't got round to reading it yet as I only received it about a week ago.
Alternatively, you can learn a GREAT deal by just been subscribed to the newsletters of Gary Halbert, Paul Myers, Ted Nicholas, and Michel Fortin. Those four copywriters are simply the best the Internet has to offer, period!
Contrary to popular belief, writers are made, not born!
Take care my friend,