iv'e bought from isellpagerank.com several times as they give lifetime backlinks and offer to replace any for free that are removed. the links they use are dofollow blog comments related to your particular niche. P.S. I do not work for or own the website and am not affiliated with them in any way...
personally I wouldn't buy backlinks, I just build them it's much more effective long term and google will love you for it. Buying links is open to abuse and most people get ripped off.
Buying link is one of the option. But most of the time people would try to build link naturally if you want to have a long run website..
If your competition finds out you are buying links they can nark you out to Google. And you guessed it, Google does not approve of buying or selling back links at all. Good way to end up in the sand box. Peace, Herman
You can try linkworth but honestly speaking, buy link not the best way, it is better to do the link exchange