If there was no payment, I'd either call the entire deal off, or tell him he had to wait to recieve snakes until you had ALL money in hand before shipping.
Once you have FULL payment, then you can work out when he can recieve the snakes, and I would tell him you ONLY ship mon-weds, so as not to risk the snakes.
If he doesn't want to do it your way, tell him to buy elsewhere.
And low-ballers usually are problems. Especially when they offer ridiculously low prices. I had someone offer to pay me $700 for my VISABLE PIED female. He then informed me that HE could get them at that price at the local show. I told him that I was glad that he would be able to purchase a pied at his local show, as he certainly wasn't going to get MINE for that price.
You go!