Money is money, and if you have earned it, worked for it and are spending it you should be able to get what you want.
With that said, I agree with grimace. Be honest with him, let him know that you are second guessing yourself for committing to this purchase and see where he stands. Be straight up with him, tell him what is going on and all that.
Worst thing that will happen is you will get it and then have to re-sell it.