Backing up a short that is under contract

[Cheryl C.]

I have been searching the mls for shorts that are under contract in my desired neighborhoods. Generally, I target those that have been UC for awhile. I contact the lister and explain my situation (investor, cash buyer, can wait as long as it takes). First, I tell them that I want to be the back-up. This is where I run into a roadblock. The listers tell me that they are not accepting back-ups. Anyone running into the same proplem? Can they refuse to submit a back-up offer or are the banks behind this "policy".

Thanks for any input.

btw - I send my e-mail and a brief note to let me know if things fall-out. I got an e-mail on one last night from an agent who would not take a back-up. He wants to meet asap.