As Amelia suggests, I would also tend to be very careful when doing this. With all of the domain crowding updates to the Google algorithm lately, we've pretty much been told that Google doesn't like to show multiple sites (domains) in the search results that are owned by the same person or same company.
In fact, you'd have to go to great lengths, spending a lot of money, in order to keep those domains and sites separate from each other and it might just not be worth it. You'd need a different CMS, different hosting, different site owner, different address, different links, etc. etc., in order to pull it off.
You're better off spending that time and effort in creating great content for your site and getting links naturally because of that content, rather than actually spending time developing separate sites on different domain names. In fact, you already said that you don't have the resources to do it right, so I would stick to one site.
If you are able to create enough good content your site and get deep links to your pages, Google will reward you with doing something similar to having multiple domains: you'll have embedded links where some links are 'indented' under others in the search results.