The traffic you get from paid links will vary greatly. In some cases when you pay for links, you will get a lot of traffic in other cases you won’t. Paid links will help your search rankings in some Search Engines.
Some people are against buying links, but it’s not really different than spending money on PPC advertising. It’s just another method of promoting your website. It has it’s pros and cons. Be sure to research ahead of time how to make the best use of any budget you set aside for buying links. Every link you get has a price, whether it be the time you spent writing content that people linked to, or the time you spent finding reciprocal link partners, or the time you spent commenting on blogs, etc. Every link has a price, you have to decide what is the price you are willing to pay for the traffic you get and how to best make use of your advertising budget. It isn’t always easy and takes time to figure out.