So I do not really have a cost estimate for fixing them until after I own them. 

I would recommend picking up a copy of the BiggerPockets book, "The Book on Estimating Rehab Costs."

(if the video links I added into this reply aren't showing up just send me a message and I'll send you the links that way) I don’t agree that you need to tell buyers ARV or repair estimates.

If I can get some "while you're here" ballpark estimates out of the deal while I'm at it that would make the $1500 sting a little less. 

I got a rough idea of what I needed using my arm span as a general rule of thumb and an estimated cost.

I estimate this property needs ~$30K of rehab for it to be ready to rent.

At the time, I was working in construction/excavation as a salesman/estimator.

Insist that estimates are obtained for any work of $xxx or more and that your approval be obtained before any work over that amount is engaged.2.

What are some ways that you all estimate rehab costs when viewing properties initially?

Estimating the cost of the rehab is equally if not more important.