I'm assuming the person thinks the data is important enough to spend a bit of $$$ to make sure it doesn't go .
I'd get one of those USB 3.0 to SATA dongles, connect a 2TB SSD to it and copy the data onto the SSD. Then I'd do a quick checksum to make sure the source and destination copies were the same. Then I'd put that SSD on a shelf somewhere other than where I keep the computer where the data is stored.
Today, that SSD+dongle would likely run you about $700. It's about $500 if you break the backup into a pair of 1TB devices.
A year from now the cost will likely be half that (or less).
Anyhow, that's what I do today, though I only back up about 1TB of pics and important docs. Total cost for me is about $250.