For drain lines buried in the ground, which are expensive to dig up and replace, why would I dig up a 50 year old line to replace it when it might literally last another 100 years!

What does that middle ground look like for you?         

HVAC duct work insulation is also deteriorated.No vapor barriers installed eitherSome fungi/mold growth notedPlumbingMultiple small leaks under sinks and from bathtub and toilets.House has Polybutylene plastic plumbing which is dangerousMain shut off valve is damagedElecticalSome small exposed wiring and bad splicing.Whole house has no GFCI's or grounding outletsInteriorMoisture spots on ceilingExteriorLose Vinyl SidingDoor Jams and Window trim have moisture damageDriveway need replacementRoofingMinor leaks noted in atticRecommended to replace roof covering, but not whole roofSome fungi growth noted in roofSo some of the question I am trying to tackle with this work is:How much should I budget for the main issues listed? 

I'm grateful both of them are remote so I can be with my family. 

No matter what you do, you cannot replace the value of boots on the ground so the next best thing(in our experience) is spend some time down there, interview some potential handymen etc. and forge a relationship, we have multiple that we have connected with in person and when you make a personal connection with them they will take care of your property better, especially in an emergency situation.

I have had first time investors purchase short term rentals from out of state while working full time, and they either elect to run it all by themselves after developing a boots on the ground team, or they hire it out to a competent manager and let them do a bulk of the work.

Quote from @Daniel Loane: Thanks everyone, very grateful for the community and the great info you shared with me! 

Just the basics, little shampoo, conditioner, soap and lotion bottles in each bathroom, salt, pepper, cooking spray, coffee grounds, etc..

This gives me some boots on the ground.

I'm so grateful we found this resource.