Will these domains be useful?

I have seen many expired domains which have page rank from 1-5 and I can grab for myself. As we know during the link building the link on the higher page rank gets more importance. If I buy these domains and add some content about 5-10 pages and use them as my blog network to build some links for my money sites.

Will those be useful in that context? I'm wrong please point me in correct direction.

Is it a Good idea? Yes and No. Blog networks are really good if you are gonna post high quality posts and use it for yourself only (don't give out the blog network) on the other hand, Google are really focusing on them at the moment, so there are lots of footprints that you can leave behind. One of them is having the same hosting for these. You need to have different hosting in different location's and this can cost some $$$.

thanks for replying