SEO is a Small Part of Running an Online Business
Many sites believe they can exclusively depend on SEO as a business model. These sites are also the ones which are typically hurt the most when search engines make significant algorithm changes.
Do not design your site and business model exclusively around search engines. Create a useful site for visitors which also is well coded for proper search engine placement.
If SEO is your entire business model you may want to change your business or you need to be prepared for extreme risks. Good businesses also develop brand and other intangible assets which enhance the value of their business.