Plumber

Another shout out for James @Leo's. I've known him for years and he's done a number of repairs at my house. He knows his stuff.

I'm curious why some plumbers didn't want to do the required work? Is it because the lines feeding into the large cast iron pipe from above also need to be replaced and would require tearing into walls? Aside from James @Leo's, I've also used RJ Carroll (they have been reliable/professional but pricey) and had Lee & Sons replace a sewer lateral which required trenching.

TJ Rooter Solutions did ours. They starter with the best price for cleaning the sewer pipe and videoed it for free. It was it was found to broken cast iron and they ran from the foundation to the D/W because of the City (SB) was waiting to line along the street. I personally checked the area under the floor with them and had them replace that also. When the City was done with the lining and screwed us over having to do from the D/W to the main Rooter Solutions saved us several thousand dollars by having Economy Plumbing do it. We had no choice as the City said we had a chip at the tie in and fix it or pay fines for hundreds of dollars. Even worse, after we had pay another 7 thousand the City quit making the home owner as from what I've heard.

TJ, you've got two strikes against you. It's in the crawl space and you only want to replace a small section of 60 year old cast iron pipe. It's a lousy small job and they sure won't want to give you a bid as there are too many unknowns. You've already had six plumbers reject your job so far and you're competing with nice, clean, and very profitable kitchen and bath total remodels. Sorry. Consider biting the bullet and replacing the cast iron main line all the way to the street with ABS. It won't be cheap but you'll need to do it someday. If you can't manage this then offer time and materials so the plumber won't lose money when your job turns sideways. Don't get sticker shock when you see $80-100 per hour. Good luck.