It depends on what you want to do with the picture. Do you want to e-mail it to your clients, post it on your Web site, print it on a magazine, or a direct mail piece? For images that will be viewed on a computer monitor (such as those you send by e-mail or post to the Web), a low pixel-count setting is perfectly adequate. Since most people view images on monitors that display only 800 x 600 pixels, a low pixel-count image, such as a 600 x 400 photograph, will fill up most of their screen without running off the edges. A low pixel-count setting will also reduce the file size of the image and reduce time it takes others to download or display your image. Printers, however, can print at much higher resolution than a typical computer screen. Images that you intend to print should be captured at a higher pixel-count setting.
- For a 2″ x 3″ print, the image dimensions should be 400 x 600 pixels minimum = 0.24 megapixels
- For a 4″ x 6″ print, the image dimensions should be 800 x 600 pixels minimum = 0.96 megapixels
- For a 5″ x 7″ print, the image dimensions should be 1000 x 1400 pixels minimum = 1.4 megapixels
- For an 8″ x 10″ print, the image dimensions should be 1600 x 2000 pixels minimum =3.2 megapixels
as you can see, you don’t need a 7.0 megapixel camera or above that will cost you muchisimo dinero to do the job right (provided you a not cropping the image too much). Any good color quality camera set up around 1.4 or 2.0 megapixel resolution will do perfect images for printing and you can always down-size it for screen resolution use (Web only). 
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