Ive had some of my listings not post as Sold on Zillow for sometime after there sale. Not too sure why this happens. Yet, typically they get their info from the MLS and post with in 24 hours.
From a first time buyers perspective, I wouldnt waste your time with short sales. Usually there are standard sales or REOs in your market place that are a much more viable option. As an agent, I dont show short sales to first time buyers because there are so many factors involved that get in the way of that buyer actually getting that particular home. From an investors perspective, with 25%+ down payment or all cash, I would look at this option. Typically you are not in a rush and can wait 2 months+ for a decision on a lien holder(s). Currently I working about 8 short sales and have been working them for the last 3 years. The process for approval has been cut down over the years, yet a first time buyer today can get quite frustrated with the whole process and dont recommend it.
To my understanding renting it back from the new owner should be ok. The banks approving the short sale are more interested that the actual sale is a Arms Length transaction, and buyer and seller do not have any connect. It doesnt speak about after the transactions and renting it back to the previous owner.