Short sale questions for newbie

[Alex K.]

I put in an offer on a property for 450k and the comps say at least 600 and up for similar properties . But , the agent wants all cash offers only for a short sale !? Why would an all cash offer matter for short sales ?

And the property has tenants and the listing side would not let me see it as a buyer before putting in an offer and getting it accepted first .

Have any of you experienced anything like this ?