Re: Used Safe
If you're buying a used safe, don't even bother looking at used gun safes. Look at commercial safes that have been refurbished or at least serviced (or get your own safe tech to do service work). You want to make sure the UL-grade locks have been serviced and the hinges are in good order. Checking all the relocking mechanisms and doing a once over would be good for peace of mind. If that work hasn't been done, find a SAVTA or Clearstar Security network affiliated safe technician to do the work. A malfunctioning commercial safe can be very expensive for a tech to open. I'd be wary of letting just any locksmith touch them since the mechanism internals of commercial safe units are kept fairly secret in the safe tech industry. The good thing is commercial safes tend to be dirt cheap because they're heavy as hell and most new businesses that need a safe aren't going to look at used safes.
Gun safes are a joke by comparison to commercial safes. There is a reason that comparably-sized units tend to weigh several times that of the sheet metal or thin plate gun safes. If you can swing a Mosler and convince the landlord, that would be a fantastic investment that will last you a lifetime and offer far more protection than a consumer-grade gun safe.
Other common brands to consider that commonly pop up on the used market would be Diebold or American Security (their commercial line). Less common brands like Kaso, ISM, Tann, Rosengrens, Chubb, Tann, or Fitchet show up on occasion but they tend to be used by high-end jewelry or numismatic businesses. They're all made in England, Israel, Scandanavia, and the like.
There are some new companies too out of the far east that sell cheaper commercial safes (by comparison to the established players) but since safes tend to be long term investments, you probably won't find these on the used market yet.