Can I start settling into a Condo I'm buying for a Short Sale?

So I'm buying a condo and it is a short sale. I put the offer in several months ago and all signs point to a closing date in the near future, but short sales can really drag. I'm in a sticky situation though. I'm getting married in a month and I really want to start to work on this condo before the wedding, such as painting, cleaning, and possibly furnishing. I personally know the owners of the condo but they stopped paying on their mortgage so their bank is running the short sale. The condo is vacant but the owners still legally own the condo and gave me permission to start doing what I want. Is this legally allowed? Do I need the bank's permission?

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