Some reading into studying SEO and link building my question is: I have been approached by site which would like to sell me his sitewide blogroll link for some $$ per month and the blog is good and regularly updated one and so would like ot know if I should get the link for some $$ per month
Buying links is not good idea, it is considered a part of black hat SEO. Even you should perform strong and useful seo activities to improve site's PR and backlinks. Thanks Franky
Isn't paying for inclusion in a directory "buying a link". Almost EVERY SEO book that you will read will recommend including your site in a yahoo directory which is pretty expensive. If it works for you, and worth the money, knock yourself out got ahead and buy the link, and i just don"t get how google will "find out" that you bought the link?
buying links in a blogroll is ok, I saw a lot of competitors doing this and it works very well for them. Also, google will never know that these are bought links, how they could? Links you don't have to buy are those in well-known links sellers, not the links you see in simple blogs with 8-10 text links in their blogroll.
I also don't prefer buying links. But if the site have massive visitors then it can be effective for traffic. If google finds it then it is forbidden.
I would not recommend link-buying. Reason being that the search engines can detect that your links are coming from paid sources or link farms. They will stop ranking your website even if you discontinue the act. This will harm your site in the long run.