There are forums and websites that offer footer and sidebar links as means to support their website. Here the links usually have dofllow property and potential visibility on the page. So many people tend to exchange or purchase links on those forums. Though value of link depends on the value of domain and the traffic that site gets. However this can be a good funding method for websites that can showcase other bloggers and forums on their site.
Do you think Link sales is a good way to fund your website or blog?
Ha ha, this is a terrible way to make money for a website! Well, technically, it's not illegal - but everybody wants to rank on Google - and Google penalizes this harshly. OK, well, if you add a "no-follow" thing and your just probably selling traffic, then you can do this with no penalty threat.
However, though, there is this thing with selling blog posts - and, often, it's just another type of link buying. I don't get it. Does Google punish that? Do they punish directories? Well, they do - but only low-quality ones!
It's a good idea if you have the customers and users who are willing to purchase advertising otherwise you'll have to look at alternatives ways to fund your project.
I'm not to sure if Google would apply penalties for the website(s) involved in link building. You may want to read their terms and conditions before you plan on doing anything.