Actually, that's not how I see it working.
If I put a future "available from" date in the resource information dialog, stating 100% availability beyond that date (May 1st), then no "available to" date appears in the resource sheet, as there's nothing telling project that the resource is not 100% available already. I have to specifically tell project that availability UNTIL May 1st is zero. It seems by defauly project assumes 100% availability unless advised otherwise. Perhaps if I could reset the default behaviour to assume 0% availability unless specifically advised otherwise, then what you say above would be true.

In my case, though, "Brian" is actually a piece of test equipment which we are looking to purchase. The "available from" date should be the date we receive the equipment from the supplier.

Is there a table view which shows all such resources, and will allow me to set, or at least view, the first date on which Brian will turn up for work- rather than having all resources listed, but have no visual clue as to when they will be available for work?

thanks
Guy