Not sure about that, yert66. Everything I have purchased (read apps) had to be downloaded. If you do not need to download it right now, why not wait to purchase it?
If you use iPhone, Mac, and tablets, etc., they all sink with one another. I do not see how you could buy it without downloading it. That would be similar to paying for a ticket at the theatre but not going inside to screen the film, yes? I think you can now buy tickets in advance, but I do not think it is possible to buy a ticket for "anytime" you feel like seeing a particular film at the theatre. Why would you not want to download it now if you want to purchase it now??