How do you cost a rehab?

[Jenna Lee]

I am a new investor that's really trying to get into real estate investing and I am so happy to have found this forum.

One of the market that I am looking at have tons of distressed properties that are either a teardown or in need of major rehab. 

So as an investor, when you go into a potential house that you want to purchase how do you estimate the repair cost? Do you usually bring a contractor with you when looking at potential homes? Is there services that you use that give you those figures? Or is there a software that you use help create cost estimation for you?