said 1 year, 3 months ago:
I agree with @casmccullough. You definitely need to pre-qualify potential guest bloggers. If you let any and everyone post to your blog, regardless of the quality of posts, then your site will end up looking like any other blog in a blog network–many posts, low-quality content.
Google has been de-indexing blogs on blog networks left and right of recent. They don’t provide value for anyone.
For SEO purposes, you don’t want a plethora of outbound links without accruing inbound links. A serious guest blogger will offer to push their guest post to their audience (you can ask or encourage them to). Those who spend time writing a quality post will definitely want it read, so they will most likely send it through their social channels. That push should provide the necessary reach for others to link to the guest post, thus providing buoyancy to each post.
Tip: Create an advert on your front page inviting visitors to become guest bloggers. If the purpose of your site is for guest bloggers to provide the content, make sure it is well known throughout the site and via each post.