I wouldn't buy a stock pump, new or used (especially used). After we burn up the stock pump, many of us switch to the Turn One pump, which starts as a stock pump, but is modified to survive high RPM use. The steering will be a little stiffer at idle, but even the very light throttle you would use while parking is enough to get normal power steering. It really isn't noticeable in everyday driving, and is very streetable. It also runs MUCH cooler than the stock pump.
This is one of those do it right the first time or you'll do it again later situations

If you do go stock, use Redline PS oil for your best shot at keeping it alive as long as possible.