This is a little bit on the grey hat/black hat side of the spectrum. But the fact is building a blog network with expired domains flat out works. The only issue is getting those cream of the crop domains without going broke. This video will walk you through tested strategies and techniques you can use to find powerful, yet affordable, expired domains.
If you buy a dropped domain from Snap or Namejet, the backlinks seem to be worthless for SEO.  They are valuable for traffic if it's targeted to your site.  Go ahead and 301 redirect into your site because it's the traffic from the back links that is worth something.  I use the Google URL builder to redirect these names so you can see the domain the traffic is coming from.

I did this last month, snagged a great domain that no one else found and got it for $69 because I waited until the last moment to place my pre-bid. Flipped it within a week for a little over $1,000. And probably could have gotten more if I sat back and waited 6-12 months, but a bird in the hand… (plus I like to keep turning over inventory and maintaining cash flow).
Once you’ve settled on some domain name ideas, you can head over to a bulk domain search tool such as DynaDot’s to mass check all the names against different TLDs. When you’ve found one (or a few) good candidates, you can simply go ahead and register them for approximately $10 each. The next step would then be to market them. Then finally, it’s a waiting game.
Let’s play this out with a real example. Say you’re familiar with the real estate market in Tempe, Ariz., and you have the opportunity to purchase for $200. This might be a good deal. Tempe has a lot of rental property; it’s  a competitive market; and there’s ample turnover in the apartment space because the city is home to a major university. Ask yourself:
For the following TLDs you can now find a expired/deleted domain list. .gi, .gl, .gy, .hn, .ht, .ky, .mu, .om, .pf, .qa, .rw, .sb, .sm, .sn, .st, .sx, .tc, .tl, .ug, .uy They also show up in the Deleted Domains (last 7 days) list and in the Domain Name Search, however they are not in the pending delete list! I do not have a working droplist for them yet, so that is why they are not released in the pending delete list yet.
Using the keyword search feature you’d also be able to familiarize yourself with how much domains typically cost on average in a certain industry or niche. Even better, they have an addictive little app called “The Domain Game” available for iOS and Android. They basically give you a domain and you try to guess whether it sold for three, four, five or six figures. You get points for each correct answer and lose points for incorrect ones. You do this for a while and you start to see patterns. Your brain starts connecting the dots and you get better it. Now you’re ready to go out there and scout some domains!