Both Mack1time and Jeff are 100% correct. You should have it spelled out clearly in your terms page. Something like "25% non-refundable deposit required to hold any animal with balance due in 30 days unless other arrangements are made.
Once you are in the situation, you need to contact them, either by phone (IMO best) or by email to find out what's going on and to give a deadline. If by phone, follow up immediately with a email "per our pone conversation we agree......" to have a record of what you agreed on.
I had a couple snakes in the exact same situation this year, sold, no deposit made, told payment was sent and excuses why it was not. Set the deadline as I had another party interested and when the deadline passed, transferred deal to second buyer who basically did the exact same thing. Ugh!! When a third buyer expressed interest, went through the process again and when that deadline passed, transferred deal to the third person who promptly paid for them and shipped them the next week.
Also had other deals where the original buyer never responded (moved to Mars?) and eventually put them back up for sale. Unfortunately it happens a lot and is why I address it in my terms page.
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Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC and still very fiesty)
0.2 kids (CBB, a big part of our selective breeding program)
LOL, to many snakes to list, last count (02/01/2010):
42.61 BRB
27.40 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 

