Funeral home. You'll never have a lack of clients. Ever. Just be sure to have a reasonable price for your services.
Storage lockers are a pretty bullet-proof business, especially if you can pull off the zoning to build one in the right area. I'll never understand why people hold on to their junk so dearly but they do and that's about as easy a business model as there is.
I have a stash of (personal) Class III/Title II firearms in a high-security storage unit that can be accessed 24/7. Look at the multiple on PSA!
That would make for a great "Storage Wars" episode were you to kick the bucket unexpectedly and your locker comes up for auction.