Detz,
You don't want to do that. And, I doubt any serious copywriter would bother doing it also. Here's why:
First, you only hire a copywriter for one thing... sales. So asking a proven copywriter to just come and "fix up" what you've already done could be a potential nightmare for the copywriter. The reason being, what you wrote, with all due respect, may not do a convincing job selling your product or service.
Therefore, the copywriter would either... A) Have to rewrite the entire package... B) Quit working with you because they know it won't work... C) Do a crappy job trying to use copy that just won't sell... D) All of the above
Also, copywriters don't cost you money, they make you money. They know it. That's why anyone who knows doesn't mind charging from the mid to high 4 figures to 5 figures for a "simple" sales letter (which is never simple).
Look at hiring a proven ad writer as an investment. You pay upfront for a greater return in the very near future. Sometimes just weeks! Don't think old Buffet could even do that. Been reading a lot about him.... he spent mucho time in analysis, then he moved... and moved big. Great marketing lesson there.
Hope this helps you out.