Shingles have 

Chances are there are already multiple layers so there's no cheap lay another layer of shingles alternative when it's time to replace.None of these are show stoppers, I personally LOVE older houses... but just things you need to plan in a little more for.

Hardie is more durable, but also more expensive.I removed all the old shingle-style siding from my house, and replaced with the LP.

The roofer wants to tear off existing roof (only 1 layer of shingles) and replace with 3 tab 60 mph rated shingles.

I regularly save all paint, tile, some 2X4, maybe a bundle of shingles. etc.  

He's saying those prices are too damn high.Replacing the shingles on my 1300 sq ft SFR is about $8000

That way we have WHAT we expect from the contractor IN WRITING, and there is no less arguing about money during the course of construction.We also have a computerized scheduling system  that helps keep tabs on multiple jobs and helps streamline communications to everyone on our team including our subs.  

When I have been able to meet face to face with someone and explain the reason for the foreclosures, they're usually forgiving, but when it's a computerized credit check, I look horrible.

The subject of putting a metal roof over an existing shingle roof was discussed.

The design life of plumbing is about 60 years, a roof 20-25 (for cheaper shingles typically used on a duplex), carpet anywhere from 3 to 10 years depending on the tenants.