Shipping container costs went up after covid, but still, at their peak you could buy one for ~$5k, $500/month is insane rental price especially if he never moves it.
I looked up prices for 40ft container: pre-covid: Under $2,000, Peak Pandemic (2020-2021): >$8,000; 2022-2024: prices falling, Current: $2,300
Ah, I was thinking of the 20ft, which can still be had for $1-$2k. If you are storing junk, might as well go for the big guy.
20ft containers cost almost the same as 40ft containers due to supply/demand.
A couple months ago I paid $3500 delivered for a 1-trip 20ft container just outside the Bay Area. It was the best of four bids.
Must be somewhat regional. My quick search showed some options as low as $700. Could be scams or nothing but rust, but still seems possible to get options well under $2k