If a stand is available to borrow then by all means go ahead and use it. But many cyclists may not have that option. Buying one used at a swap meet or on Craigslist would also be reasonable since much of the cost could then be recovered by reselling it - but again, there may not be one available locally.

What I and lostarchitect were objecting to is the idea that someone who may or may not ever be interested in building another wheel must immediately go out and buy an expensive truing stand. It's perfectly feasible to build a wheel using the bicycle itself as the stand. Not quite as fast or convenient as a regular truing stand but it'll get the job done and give you a good idea if you'll want to do it again often enough to justify the expense of a real stand.

And yes, I frequently inflate a tire while simply "eyeballing" (actually thumb-testing) the pressure. But I'm puzzled by your suggestion that I wait 500 miles before buying a pump since the primary function of the pump is to do the inflating rather than the "eyeballing."