Estimating Costs

When estimating costs for repair on a deal (before making an offer), what figure would you use for having to do some foundation work?

We have a house that has an addition that needs foundation work. The addition has a crawl space under instead of a basement. One of the support beams eroded and needs to be replaced. I know that you have to be careful, especially working with foundations. It may have to be jacked up to put the beam in. Also, the chimney is not up to code. It has bricks missing in it. Really not safe for tenants. Other than that, electric is good and plumbing is good as well. We just don’t know what to do about estimating the cost for repair. The seller is extremely motivated and will to negotiate the price. Even with 20k in repair, the numbers will still work. What do you think? :help

I would call a specialist out for a ballpark figure.