This would be a warehouse to store safely and/or liquidate anything that people collect. Customers would be offered three types of accounts.
1. Safekeeping only
2. Safekeeping with liquidation efforts.
3. Stripping customer's residence of all the accumulated junk and auctioning or selling or
A weekly auction would allow speedy liquidation and a fixed price catalog/web site for when the need for speed doesn't out weigh greed. A swapping service (wine for watches say) might also make sense for some customers.
Currency exchange and deposit box rentals would be a natural fit.
Could also act as a normal bank (loans and so on) if allowed.
Would need an extremely low rent building and a gang of movers/garbage haulers. "Trash out" services is a good search term to see these folks in action.
Landlords end up dealing with collections of clutter by hauling everything to the dump, because Goodwill or Salvation Army mostly can not deal with these messes in timely or profitable manner.