Building with free links is, yes cheaper than buying them. Google may be going after those selling them, but you need to be careful where you are placing these free links as well. Don't submit to obvious link farms as that is easily penalized as well.
Well the odds of getting free links on websites with good PageRank are pretty small. I think buying just a handful on high PR sites that are relevant to your content is smart.
well all links count but matter is quality search for quality sites that can show your links if high PR site gives you a link back then iits a bonus for you.
Free links are better, because you have worked for them yourself, and because their cheaper, and because no-one can cheat you out of your money when you use them.
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