Can I send samples of his project to a buyer before he placing the order. Can I do that or is it against Fiverr TOS.
Check out this topic: Work getting done by sending samples, without payment
You can but leave yourself at risk of them taking your sample and having someone else finish it. I sometimes send samples to my returning clients or clients that I’m not 100% sure about. My conversion rate when doing so has to be in 90 percentile. One in every 20 buyers disappear.