Whatever you do, don’t make it a pattern. The easiest way to find unnatural links is to look for blog post with either
– one outgoing link, pointing to a commercial website, or
– two outgoing links, one pointing to a commercial website and one to Wikipedia or to an outdated news article on a well known news site.
Put as many outgoing internal and external links as makes sense for the given article.
Your buyers might object to too many outgoing external links. The more outdated their SEO knowledge is, the more likely they are to demand the article only have 1 or 2 outgoing external links.