1925 apt building, galvanized steel - Run or Quantify the risk?

[Stephen Anthony]

I'm very close to starting my first deal. Purchasing a multi-family property in the $200-350k range. I've identified a >10 unit property that has moved to the top of my list. Positives: $18.5k a unit, at least 12.5% under market rents, full, 4 floors solid brick, no basement, inside is clean and well-kept, conservatively (50% expenses) the financials are good. At current rents. Current owner has had it 20+ years, personally interacts with the tenants.

Cons: It was built in 1925, and is full top to bottom with galvanized steel pipes, including the main. Not sure about the wastewater. Pipes have been replaced here and there with copper as they leaked, but no renovations. Also, it's been on the MLS since December '12, is that saying something? Then again, so have 25 other properties.

My general contractor and apt owner friend says to run the other way. The pipes will be a constant maintenance expenditure, and the main is a ticking time bomb that will cost tens of thousands of dollars to replace and require emptying the entire building, and taking out the floor of several bottom floor apartments.

The math nerd in me wants to quantify the risk - what's the likelihood of the main going while I own it (I only plan to own 2-3 yrs), how many replaced pipes per year average at what cost per break, etc. I've also just learned about inserting a new plastic pipe inside the main and epoxy lining all the pipes. Expenditures for sure, but ones I could quantify ahead of time and perhaps plan on doing immediately, as insurance against disaster.

My friend says to avoid *everything* before 1970. He also tends to do all work himself, so I feel like the hassle biases his thoughts. I like getting it down to calculated risk and numbers. Thoughts?