This is just a general question for commission artists as I've encountered a situation I never had before. I usually pay immediately or well in advance to an artist (that I trust) when it comes to buying commission work. I recently ordered some custom metal work, from someone. He lets customers know immediately that there's a long wait period up to 10 months, and then once the product is made they pay in full. This person doesn't take advance payments. Most people take full payments immediately before anything gets done, so I'm a little surprised.
The only reason I can come up with is perhaps to avoid chargebacks and paypal issues?