Too bad I can't afford commissions.

That's kinda rude of people. If you tell an artist that you'll pay them....you've essentially bought it already. Do the right thing. Now if something comes up and you haven't got the money, tell the artist, especially if they started working on it. If they haven't they're usually pretty ok with it. That just means someone else can buy their art.

Indeed, that sounds immensely annoying. As a rule I treat commissions the same way I do ebay purchases; know that you have the money and pay immediately.

I generally get the payment in once the price quote is sent, or give a time-scale for when to expect the payment.

i really want one yet i don't know how to pay for one