Odds are being this close to the
PR update it will lose some or all. If you buy after the update you stand a good chance of retaining the
PR providing the site created is worthy of the current
PR.
i.e. People pick up the PR4 names and turn them into word clouds most of them end up with a PR0 at update time. Though some only lose some. My experience was a PR4 dropped to a PR3. So do your research on how many many backlinks it has still and with some luck some edu backlinks.