Who to bring with you to a walkthrough?

We brought a couple of GC's to help gauge costs. Of course, your costs will shift depending on the finishes you choose, so you should have an idea how high end you want to go and express that to your GC to consider when giving you an estimate.

You can get a ballpark price by just emailing contractors your floor plan with a scope of work. You do need to explain the existing conditions (do you need the walls skim coated vs. just painting)

I brought a contractor before I placed the bid on my current apartment, not at the walkthrough. He outlined everything he could absolutely tell had to be done and gave me a very rough estimate based on mid scale upgrades. He pointed out problems with the walls that I hadn't noticed that made skim coating necessary. He gave me a worst case scenario if I needed extensive plumbing and electrical work done since nothing had been touched in 60 years (still had fuse box). When I bid out the work, I found he was fairly accurate.