Stay away for Getty Images... these are usually exclusive images AND they will come after you - and they will not care that you "paid a designer to create your site". They will demand a license, and charge you a huge fee.
Here is a safer way to use this technique:
Look for images that appear on TWO royalty free sites.
For example, image providers will "sell" their images through dreamstime AND istockphoto, therefore it would be difficult for either company to come after you as you could argue you bought the image on the competitor's site.
Usually, the artist will use the same image name/description... and even the same username.
Look for images that have been sold at least a few dozen times.