If its sounds shady, it is...

I suggest you think of the user... seo is crafted like a book. Provide unique content and give credit to those along the way who helped.

Hiding the info to show, hey guys I gave you a link, give me one.. is shady IMO

Yes you can do that on linkmarket. The problem with link market is that everyone does that so the links are basically useless. If they do put your link they homepage or a page that is within navigation, many times they will remove it after a few days when they don't think you will check back.

I've done that just with directories that demand a backlink to list you. Those links would be of little use to people who visit my sites (ie: promoting internet marketing to depressed people - {oh, that could be funny} ). Those sites really wouldn't get much benefit from links from my site to theirs.

I do not do that with real sites, like sites that can give me a link to use that goes to sections that are relevant to my own site. I set the irrelevant backlinks on a separate page that has a less obvious link elsewhere on my site. Relevant backlinks go on a page with obvious links on my main nav bar.

Another way around having double linking is to offer to put their links on one of your other sites. I've done that and it works fine.

Sylvia