I wonder if it can harm my site if I buy a blog post for it from a blog created on a dropped domain? E.g. I have an opportunity to get a link for my automotive site from an automotive blog which is PR5, but it is obvious that it is run on a dropped domain as the domain name has nothing to do with cars. Can such link harm my site? Or is it not a problem?
When you say a dropped domain, do you mean a domain that has been penalized and dropped from the search engines, or the original owner has dropped it and it now has a new owner, or is there something else you mean by dropped?
I mean that the original owner didn't renew his domain and someone else registered it and created a blog on it with different content that there was before the domain dropped.
If the site the new owner created is similar to yours then it is probably ok, but if the previous site was similar to yours but the new one is not then it will most likely not benefit you as much. When a site changes owners or the type of content it is about and the search engines learn about it, they reset most of the authority and trust measurements for it, so if it is a recent owner switch or content change, which Google knows about, and it took place after the most recent PR update then it is likely that the real PR score is much lower than what is shown. If the site is related to yours and shows up in the search engines, then I would not worry about it, you should be fine. Just be careful to not get caught buying links.
There is always a risk based on what the site does that is selling the links. The best answer to not get caught is to not buy them, but that is not always realistic when you have to compete with other sites who are already buying links. You greatly increase your chances of not getting caught by buying links on relevant sites related to yours and getting links within content or articles rather then in the footer or sidebars.
Thanks for your reply. That actually is what I'm doing - I'm no longer buying sitewide links, but I'm buying blog posts only.
There is no harm in buying it. But the entire blogpost should be related to one niche. I am seeing few peoples have some domain name and put blog posts of all niches.