Guest posts: paid articles, priced by metrics.
You or the vendor writes an article, the site gets paid, and your link goes live. Typical market rates run $100 to $500 per post, scaling with DA. The upside is certainty and volume. The downside is what certainty implies: sites that reliably accept paid articles are running a business Google explicitly targets, and under its rules paid links should carry rel="sponsored", which strips the ranking value you paid for.