Do articles need to be perfect for SEO?

I recently outsourced some article writing for my mini sites, and the articles aren't perfect. They are definitely readable, but some of the words the guy I hired uses are just.. different. English isn't his first language but he works for an extremely low price.

Do the articles have to read perfectly for SEO purposes? Is it worth spending more money to make sure the articles read perfectly?

what do you mean perfect ? is it readable without making somebody confused? are the keywords in the right places? does it pass copyscape? if the answer for all above is 'yes' then i guess its good enough to go through.

Yes, it's readable enough for people to understand, but you can tell it was written by someone who's native language isn't English. The keywords are placed well enough so I think it will be fine. Thanks for the feedback!

there is no need for perfection here.it does not affect seo at all.I assume that you are going to use an adsense ad just below the article title.so that would make no difference.But understand that if your minisite is an affiliate site then it is better to use proper English and use good preselling pages.

agreed, articles don't have to be written by University professor. The purpose of articles is to gain exposure and links to attract SEs and human visitors.
With that in mind we aim to please both, as long they are written with gripping / interesting enough content so the humans want to visit your site and as long there is proper keyword placements, uniqueness and on topic content the SEs will love it as well.
If you were to write PR articles and wanted to get attention of investors for instance the ball game would be different, in that case you would have to produce virtually perfect content.

Do not forget to optimize your landing pages for both as well, I sometimes made mistakes of focusing too much on the SE that I would end up getting good rankings and traffic but the ppl would be like WTF?/?.
As always that is my opinion and I am sure there are many thoughts of school on this topic.

The only reason why your article needs to be perfect is to attract the human readers. For SE, as long as the article is written in english, made some sense and is "unique", it will be fine. It works out that way for me.

NO! they dont need to be perfect- but make sure the first 35words are perfect and what gives the more information -and attracts people! Since those first 35words will be shown at google when people will search for your keyword- So it's a must!