How do you personally estimate your rehab costs?

[Frank Cole]

Hello,

Relatively new to investing, and am having difficulty in ball parking repair costs when making an offer.   For you experienced DFW investors who often may even make an offer on a property site unseen, is there a formula , you use to guestimate how much a rehab will cost

(e.g. "x" dollars times sq ft. + big 5 (foundation, plumbing, roofing, HVAC, electricity))? How does that change between rehabbing for a rental vs. rehabbing for retail?

I'll be using a general contractor, and currently plan to flip properties.

I realize that I need to verify my numbers during an option period or prior to making an offer to a wholesaler, but am trying to get a good starting place prior to dragging a contractor out to the property.  

Any and all thoughts are much appreciated!  Thanks!