I actually came across this same ad. If I'm not mistaken, it was on Craigslist. Anyhow, I passed up the opportunity, although the pay seemed very lucrative. It just seems like a gimmick to me, especially considering the long wait time to be contacted. I'm not sure, though. Perhaps, they are just very busy...
Actually, it depends on your current disposition in terms of work. If you want this work bad, then there is nothing wrong in sending the requisite sample. You yourself have mentioned that the company is legit, and their offer of 5 cents a word is fair. Worth a try, but again it depends on how much time you have to spare.
There's definitely something wrong with it. 1. Doing anything that reeks of desperation as a freelancer lets the buyer know they can walk all over you in the future (it happens often, especially on the lower end of the pay spectrum). 2. 5 cents per word isn't exactly anything to write home about. It's definitely within the very low end of pay spectrum I mentioned. Just because something's higher than what you might find advertised in garbage freelance marketplaces or forums like DP doesn't mean it's "fair" or worth making exceptions for regarding free samples. 3. Any client who asks for custom samples without paying for them is acknowledging up front that they neither know or respect what you do as a freelancer -- not the kind of company you should be doing business with. What wouldn't be "wrong" in a case like this would be for the writer to contact the company, point them to their portfolio and kindly explain to them that only paid for custom samples can be created, as their time is one of their primary assets as a freelancer. If the client understands that their request was inappropriate to begin with, they'll review the existing work instead or offer to pay for the sample article. If not, there are far better clients to pursue out there, and plenty of them (for anyone not too lazy to go out and get them).