I have website A with a PR3. I build website B. Both sites are related in the topics they discuss. I put a link on all the pages of website A, saying something like "sponsored by website B" pointing to website B. Will this help Website B to get indexed at Google? How long will it take to get picked up? Will it have a PR?
Dedicated IP numbers are generally a good idea, but I haven't had a problem so far getting sites in on the same IP number when they're linked. One site has a link from a PR5 page on a site on the same IP and just one more link from another site (different IP) that's from a PR4 page. It definitely needs more links, but it's in there with a PR4 and has a fresh date next to it.
PR3 could really stand a boost, you might start looking for more inbound links to both sites.
I don't know that I'd be comfortable with cross-linking them back and forth, and if they're similar make sure they're not duplicating content.