One more piece of information is the Nofollow attribute, it is only a recommendation and such a link can act as dofollow.

Backlinks should always be sourced manually.

Here is a list of such a service providers, https://www.fiverr.com/gigs/dutch-backlinks

Then it becomes a business requirement to have separate websites.

Then it becomes a business requirement to have separate websites.

Also, if they are 2 completely different businesses?

Besides the above mentioned, use such a content on your webpage so that people can link your webpage. This works wonderfully.

I recommend to maintain only one website rather than multiple websites. With one SEO effort, benefits will be shared with all the pages on the website.

When a website links an another website then the linking website passes the link juice to the linked website irrespective of whether a link is declared dofollow or nofoll...

Subdomains and domains are treated as two different properties by search engines. Both should have separate robots.txt files etc. As @ms mentioned, if the content on bot...