Hi Tanveer,
When you say there is login areas, how much of the site will be publicly (and therefore Search Engine) accessible?
If the content level is low, then it will be easy to keep things compliant, and the many guides on here will help with that, heading tags, meta tags image alt tags and all the good stuff etc.
Moz's new cheat sheet is a great starting point: https://moz.com/blog/seo-cheat-sheet
Is your client base already established? Or are you looking for these sites to help build it?
If content such as a blog is not available to you from management then a PPC campaign might be more suitable?
Kind Regards
Jimmy