I've been wondering, is it bad to sell too many links on a website? Do the links you sell on your site lose their value if you have too many links on the site?
if google thinks you're a link farm, yes it's bad. As i rule of thumb i have no more than 5 external links per page on my sites.
More than 15 links can be a problem. If you are going to sell links tell your site url by PM and don't write it donw to ypur thread
Don't forget that it depends on the quality of the links and their relevance too. Try to link to quality sites closely related to your niche and limit their number to max 20.