First you need to determine what are the purpose of the articles you need.
Are they to be submitted to an article directory, if so which ones and what are the standards set by the directory?
Are they purely for backlinks and fodder for the search engines?
Then you need to determine what your budget is. There is no point in asking a person who charges more than you're willing to pay to write for you.
You also need to look at what the term quality really means.
I've seen many people saying an article is quality, and nothing could be further from the truth.
But, the reality is simple ... quality is in the eye of the buyer.
They know the standards they have, and anything below that standard isn't quality to them.
What you have to remember, you will not get a Stephen King quality writing for $1 an article.
You might find someone who is good who charges low prices, but that is totally different.
Where do you go to get articles?
Again it depends on your budget and needs.
Check our the warrior for hire or WSO for your first stop.
Then go to the freelance sites.
Hint you might even try google to find some websites.
Do you need something outside of the norm for your articles, then just tell the person you hire what you want.
You need to know your budget and work from there. If you don't have a budget then the easy answer is to write yourself.