http://www.petstyle.com/dog/health_well_article.aspx?id=232§ion=Dog%20Health%20and%20Wellness
The ONLY reason i've heard people give to not neuter there dog (outside of breeding) is that it might change their personality. This is a load of bullshit. None of my dogs have ever had a personality change. Nor have i ever heard of such a thing from any other dog owners.
If you cant afford the procedure, there are organizations that can help you. If you are still unwilling, then why do you have a dog in the first place? Dogs need responsible people as owners. If you can't handle the expensices, care or time this procedure would involve, you certainly wont be able to help your dog when they really need you later on in life...
There is no practical reason to not neuter your dog.