Yeah, sink, disposal, and toilet are no brainers. Honestly, it's entirely possible that they're fixable but he doesn't want to deal with it due to the minimal profit on repairs vs upgrades.

New hot water heaters require an efficiency rating that requires the vent. Even with that however, it's not that big of a deal.

If you were closer, I'd do the labor for a few hundred bucks and call it good but I don't have the overhead he does. I'd suggest asking around among buddies/work and organizing a work party. The skills to do this work aren't rare.