It's legal and it's pretty standard.
However, that still doesn't address whether it's a scam. If the deal seems too good to be true, it's likely a scam. If the "owner" is out of the country, it's a scam. If you have to provide substantial money up front (more than a few dollars to run the credit check), it's a scam. If you're supposed to pay by mail order or wire transfer, it's a scam.
Hope that helps.