The problem isn't one of ethics.
If you just cut and past free content you probably lack the focus, that is required in your nitch.
You have to focus on your costumers instead of searching for an easy way to make money online. Does your site create added value for your visitors?
I subscribe to lifehacker because they search the web for good Personal Development posts and I don't have to read all they blog they read but can still read good posts from them.
They filter out the junk.
If you just look for free content and gather that on your website, you serve your visitors the junk.
Why should visitors visit your site instead of the other sites that publish the same free articles? Where do you add your bonus value for your visitors that distingushs you from the other sites?