Used servers are exactly as what the name suggests. All used servers comes with 3 months HOSTMINE Warranty, unless and otherwise specified. There can be issues with the servers’ physical appearance and maybe a bit more noisy than usual, but will always perform the same in terms of hash rate and power consumption. But since they are used, you can expect them to be a little fuzzy on its physical lookout.
They are always cheaper than the new model servers and can be a good buy if you want to initially only plan to invest a small amount into crypto mining and see how it works.