if you can't afford to pay someone to do the cover for you, then you might agree to exchange services with them in exchange for their design work..e.g. provide backlinks to their site or do some promotion work for them etc.
If i was going to design a cover i would probably buy some stock photos of some business man etc and then just whack a few big titles across the cover and that would be it. just "borrow" from the style of other books in your niche. maybe download some fancy free fonts. there are lots available for free.
Google "Big Stock Photos". You can buy pictures for as little as a few bucks. They even have blank ebook covers and you can add your image over the book cover.
I bought a program for approx $30 called eCover Engineer. It is AMAZING.... You can deisgn books, boxes, magazines, cds, etc. I don't have a link but you can search it on google. hope this helps!
I use eCover3D. It is not free but pretty easy to use. I would be willing to make one simple cover for you if you PM me the details. I will not be able to turn it around lightening fast, but I am offering.
There are some Photoshop tutorials out there on making covers as well.
Use Elance. you'll get a good design at a reasonable price. I use Elance for aall my design work and I've never been disappointed. When you post your add say how much you are prepared to pay, be firm about the price, someone will come along and offer to do the job for you.