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Hey there, I think some of the responses in this thread will give you what you need but just wanted to chip in. Guest posting is a bit of a contentious topic at the moment, recently Google Reps like John Mueller have said that sites should nofollow ANY guest links (so that includes very reputable sites and relevant posts). As Marjin says below - I think you're on the money when you talk about relevance. If we ignore Google for a moment - is it likely that users on those sites would click through to yours and convert? If no then it's quite likely this person is offering guest posting to a host of different sites and Google probably has a pretty good idea that the site is spammy. So you're less likely to get a ranking benefit from this and you're not getting direct benefit from the links. If, on the other hand, there is a way for your site to be relevant to the sites then at the very least you could get users clicking through and converting, which is direct value anyway. If this site is vetting opportunities to make sure they are relevant to the audience it's more likely that they drive value for that audience and don't just write about anything, which means there's more chance of Google seeing the site and links as valuable. By the sounds of things, this opportunity is in the first category so I'd be inclined to turn it down. Hope that helps!

I would agree with you, there are pros and cons. One site I keep up with almost religiously is backlinko.com. Brian Dean is a popular SEO thought leader. If you checkout his post sitemap, you'll see he only has around 30 posts - one on just about every topic. You'll find that each post wholly answers his users' questions, with examples, further resources, media, and more. In my opinion, this is the direction the internet is heading. One exhaustive post on a popular topic in your industry, updated yearly, is going to outperform (in terms of overall traffic and individual ranking) 4-5 posts on one single topic. So, the pros of lots of posts on one topic might be the potential of having multiple, specific long tail keywords rank and the opportunity to have a specific and quick answer to multiple searchers' queries. But the big con is that none of those posts will have a great chance of ranking well for a high volume keyword. Hope this helps!