If you've written them yourself then there is no reason that they wouldn't pass Copyscape.

Whether they will sell or not depends on how you present these articles.

How lengthy are they?
Are they SEO efficient?
Are they keyword researched or were they just written off the top of your head?

People want to know that they're buying articles that will eat their competition alive, and when you're selling only 5 articles, I would NEVER give out review copies (at least of the actual articles). Always write another article for a sample if people want to see it, because someone WILL try to use it for content.

Also: as for the niche as Weight Loss. This niche is hard to beat and is overly-saturated based on that term. I would do a little keyword research (if you haven't) and cleverly name the articles based off of winning low competition keywords if you're planning to sell them, this will help you out a lot.

The main things people look for when they're purchasing these articles are : Uniqueness, SEO, Length And Grammar Mistakes. If you make people believe they are getting a deal straight from heaven, then you can honestly sell anything for just about any price.