SEO is free, but involves a lot of manual link building work. People are available on freelancer and upwork, but some charge absurd prices to go online and post your link to various websites, which is just bullsh*t. Best case study for me is <a href="https://redditrecommend.com/" rel="nofollow">https://redditrecommend.com/</a> where the owner experiments with reddit linking through small posts. I'm watching it gain steam.