"Anyone have a PRICE/SQFT. guideline that they currently using to accurately estimate their rehabs??"
The problem with the above is that you can't "accurately" estimate rehab costs by using a price per SF. If you want accuracy, there are no shortcuts, you must make a SOW (scope of work) and price each line item out to be accurate allowing for a % for buffer at the end as hidden or unforeseen items are not only common, but probably, especially when the rehab is heavier vs lighter.
Lots of people suggest having 3 bids from contractors but when you don't own the property and are merely trying to put a budget together to make an offer, contractors are often not going to put forth all that time in effort on the off chance you do get the deal and do hire them, so you would have to pay for the bids. That would not be efficient at all and as such, knowing how to price out a rehab on your own is essential to your success as a real estate investor working with rehabs (for flips or holds). There are many, many threads here on BP on how to properly estimate rehab costs in which I and other pros have gone into great detail on how to perform this task.