Going on hundreds of blogs and posting comments to get a few back links can be a real pain. So it is understandable why there are so many websites trying to sell you back links. Of course you should do some link exchange instead of buying them. If you are going to buy them you should make sure they are permanent. Some sites will sell the back links for 5$ per months (example) and this can become. Really cost on the long run, especially if you do so with many websites. You should always keep a track of the licks you bought Put them in an Excel document and put the cost, location and contract terms on the same line. Make sure to go and verify all your back links once per month at least. Some people will try to make easy money on your back, or just remove the back link by mistake. Create your opportunities and keep them active. Back link building is really demanding and you should go see what sites are the best back link sellers.
In the end also consider that depending on the competition you might not need to buy any back links. It all comes back to how much backlinks you need to get a better ranking then your competitors.
