1. How much will buying PR links help a website who didn't do SEO or linkexchange at all to get traffic?
2. Are those companies reliaible who selling PR links?
3. Does anyone know a reliaible company?

If a site is selling links purely for PR and Google spots them, they will penalise the site and no PR will be passed

If the site is selling links as adverts that just so happen to be on high PR pages they should be fine.

Be careful who you purchase links off. As with many industries there are some good services and some real bad ones.

Buying PR will boost your PR but it will not bring any new visitors to your website. Spend your money/time on SEO and building a quality site with lots of content.

Do not buy links for that pretty little green bar. It does not bring in visitors - as what counts is the quantity of links with keywords in the anchor text.

I have heard good things about Textlinkbrokerage.com .

I would focus on the quality of the site content itself, then the rest will follow.

Snowblind, what types of things have you heard, exactly? I've looked into them a bit and my company is thinking about running a few links through them...