How much should you spend? That depends on the people you hire. If they are going to do linkbuilding for you, then pay for a months worth of work. That should get you around pr4 to pr5 with full time months worth of work in backlinks.
Don't pay a cent. I got a PR5 website(not the one in my sig), and I spent a whooping zero cents on it. Go me! Boo buying links.
Google is going kinda hard on sites purchasing links to get PR and affect the search results. Make sure you spend carefully !! Also, its been long since G updated the PR cos maybe they are working on new algo or something so I wont suggest you to spend much.
Yeah its getting harder and harder to buy links. I would just do forum sig links and stuff like that which will bring traffic too.
Why do you need to get to PR5? A high PR doesn't automatically mean a high ranking. Are you doing it for ego?
haha. Okay buying links. I don't know. Usually there not permanent. So your site might become a PR5 then the next update become a PR0 again when your links are gone. (unless you buy them again) Forgive me if i'm wronge but the links you buy on the high PR pages I think need to permanent right?