If let's say i purchase 10-18 PR3 links, how long will it take for my page to actually be a pr3 page? Can any of you please share your experience regarding this topic?
Personally I don't purchase links so take my opinion with a grain of salt. (I've never dished out the coin) I don't think that Google will ever let you know exactly how page rank is calculated. Keep in mind: PR is logarithmic, PR 3 is probably 100 times the link juice of PR1 (I'm *assuming* a base of 10 and ignoring very blatant rounding errors.) The PR available to the public is outdated and possibly altered by Google. The actual value used to calculate your ranking is something you will never know, only if you rank. Personally I've always thought that the PR is decided primarily per page. If you rank for your chosen phrases your PR isn't relevant. Likewise if your not ranking more link juice may be for you.
Yes, there is a recipe/formula to calculate PR, and only Google knows it. As far as I know, they are not publishing the exact algorithm for calculating PR. How long would it take for you to increase PR? I'm not saying that it will be PR3, but Google updates the visible PR every quarter, so you should expect to find a change in your PR this April. Out of topic, I knew Google updates the PR quarterly and the first update this year was last January, 2008. The world is expecting the next update should be in April but there seemed to have an update last February 19-25. Therefore, I'm not sure anymore..
Just continue your link building. Although PR3 is good, try to aim for links on PR4 or higher websites so you can get to PR3 faster. One of my blogs had a PR3 after only 2 weeks and I don't think that I have that many PR3 links so no one knows for sure but the safest bet is to continue link building.
REcipe to PR = Links, relevant links to your url. As said, PR is somewhat ireelevant, what matters is SERP and organic traffic.
You can get high PR links without buying them. When I first started my Blogging with Cents blog, I did reviews that included a backlink. In other words, Adesblog offeres a backlink for doing a review of his AdesClrPicker. Tyler Cruz had or still has it where if you review his blog, you get a backlink and so on.... My blog was live for 3mths, with about 6 high PR backlinks from Ades, Tyler, John Chow, & others...and I had a PR of 5. I was hit with a 0 for obvious reasons which I have completely quit doing on that blog and have requested reconsideration.