I am trying to create a few wordpress sites to promote my main website with link development. Does Google care if the promotion websites are on the same server as the main website?
Definitely not a good idea. Google devalues links coming from the same ip adress. you better make some blogs on free platforms. they do not cost anything. Or if you can spend something more and want complete control get some cheap hosting.
Okay, thank you for you're response. I'm gonna get a seperate cheap hosting for the promotion sites. Now I have another question. Does it matter if there is say 20 promotion site on the same IP address? These 20 sites will all have links to my main website
Thats exactly what you should NOT do.! You should have different hosting for these sites. Or else you can try link exchanges with these promotion sites.
You want to have a different C-class IP address to get full value from the link. Check with your host to see if they offer extra IP's for your other sites if you want to keep them all on the same host. From what I have seen, it usually costs $20-30 yearly for an IP address. Make sure if you do use other hosting accounts, that each site is on a separate account (or has its own IP address). It isn't enough to have your main site on one with promotion sites on another host. You need a separate IP for each site. There are some hosts out there that have hosting packages set up for exactly what you want to do. Typically they will refer to is as Multiple C Class Hosting, or Blog Farm hosting.
Yes ! Backlinks from the same C-Class IP addresses (Same host) are much less valuable than links coming from a different C-Class IP addresses (different host)