I have few domains on same IP address that I am using to create pages for search engines. But to buy a product, a user will be redirected to the main domain(which is also on same IP). I want to know, doing this is fine? A number of domains on same IP address?
Yes it may be best to use separate ips, but it would still be easy enough for Google to tell that they are all the same company. You just want to watch how you cross link them. Google doesn't care if you have a few websites. They just don't want you to use them to increase the PR of your other site. How does your redirect work? Is it javascript or does the 'add to cart' or 'checkout' link directly to the main site?
I am working on an education related site. So these domains are all education websites but they differ in like accounting courses, spanish courses. Depending on domain name, content would come.
If you crosslinks are few related sites, it is not a big problem as long as the sites are related. If you cross link 100s of blogs that may be a flag for Google.
Cross linking will set off a Google flag. I call it a Sub-Net penalty aaa.bbb.CCC.xxx where a,b and c are the same. If you are doing this for links, you will get busted. Also, be careful of duplicate content. How we over came this is to create 1 link on each page going to the main site that is the PR transfer link. And none of the other sites had cross links. It would also be advisible to have your "redirect link" above to be this link but make it a real SEOed link. The traffic to the "keyword page" will also help. And go slow on building the links up. There is a good chance you will get a Penalty-30 or -90 for building links to fast.
It looks to me that you've got the right idea on separating your niches. The accounting site doesn't relate to the spanish site, but they both relate to your "master education site". So link them both to the education site, but don't interlink the other two (of course you will have some sub-sites that will be more closely related so be sure to link them). As long as you don't over do it and the links are valuable to your visitors you should be fine.
No site will be cross linked. Just links going to the main site. And also, I am not looking for link building. Just few sites with related and unique content on them for SERP's and links going to one site(main site)
Yes, I will have some closely related sub-sites..like 2-3 sites on accounting but with different content on them. Is it okay to interlink these sites? Well, frankly I was not looking to interlink any website, but just got an idea.
Site redirect may be harmful. search engine avoid. Search engine doesn't look same IP redirection or other IP redirection.