I have a lot of sites on different subjects ranging from video games to computers (but no gambling/adult websites). When searching thru different forums and website about people selling links , i noticed people do not like to buy links on websites with links to gambling/adult websites.

Does this lower your ranking? Is there a problem if you do this? Why do people not want to buy links on websites that do this?

The reason i am asking is i am selling links on one of my sites. I would never sell any links to adult (sex, etc) websites but i don't see the problem in selling links to gambling websites?

Please enlighten me.

It still depends on the theme and status of the site, if the site is a bad neighborhood site, definitely your site's ranking would be harmed.

Its not that it will lower your page rank, infact, no link can ever lower your PR. Its just some hosts have certain rules against gambling and adult content. Its also a bit unethical linking to gambling and porn websites knowing that you probably have kids browsing your website.

The only thing you need to worry about is linking to link farms and other websites that try to manipulate SERPs "illegally".

It's not bad. It does not affect your page rank. Some advertising programs (for example Adsense) consider any sort of connection with Gambling / Adult sites as a violation of their policy.