A lender brought it up to me that the assessed value is low compared to the agreed purchase price and she wasn't sure it would appraise.

It's substantially cheaper than buying a comparable single family home. 

How much did it cost, and how was the process compared to a standard mortgage?

Those numbers look good on paper compared to your 450K home, but I'm sure my west-side homes offer 3 times the stress!

Galvanizing copper is a chemical impossibility.Projected lifespan of galvanized piping is typically projected at 60 years, but it can be less or more depending on the water quality of the source.Copper is generally projected at 80 years but same caveat.Lifespan of plastic is for all practical purposes, infinite. 

You need to examine the details of your comparables to determine what the potential ARV is:Are the comparables all in the same city or village Sometimes using the radius for comparison results in spillover from another city or village into the comparables.  

In fact, it's the person you should be trying to pay more.This is the guy who brings you deals or sells your property. 1-2% on a property is nothing compared to how energized your realtor will be for you.So you knock his commission down, do you really think he'll bring you the next deal he sees?

How does that compare to a triplex? 

"Compared to what?"  

I work up a basic rehab and a nice rehab figure and compare those to my ranges.