PLR blogs are simply blogs where the rights are sold to several individuals instead of a custom website that only you will have. You are buying the private label rights llike you do with PLR articles and this usually gives you the rights to edit them. These are perfect if you want to build out your network with professional looking sites. They have the professional look of a custom blog but cost a lot less.
Just like with anything else getting a quality PLR website means buying from a reputable source. You want a professional design and ease of use. While you won’t get the kind of support you do with a custom blog, you still want to make sure the seller is responsive to questions in case you run into trouble.