My friend tried to comply but the age of the property makes it impossible to get the property up to code other than demolishing and rebuilding the whole property.

I use $/unit per year for each, and the actual amount will vary depending on age and condition of the property, the location, and the size of the property and the units.  

Be conservative in your rent projections and overestimate the repairs.I am not sure what the age of this property is, but I have found with older properties (mixed-use and apartment complexes), there are several variables that are typically not an issue with newer properties.

I get to the point of targeting a divorcing, male tenant with 2-3 kids, age 32-45, who makes between __ and ___, who currently live in ___ radius.

The first property I ever purchased years ago I sold last year due to its age and location.  

The underwriter is the one that actually does the verification so I don't think a lender can say definitively until the underwriter has done their thing.

I would do it again for sure if I was still in my early 20’s and single, but not at my current advanced age, with a family. 

We tried to get info on the lender to ask directly but they wouldn't give it to us.I would have thought this would be a relatively quick process to do a credit check, check debt to income, employer verification, etc.current loan's interest rate is very low so they definitely haven't refinanced anytime recently.Additionally, having never assumed a loan before, anything I should keep an eye out for that might cause a hiccup? 

It depends on a few things:1) Climate - if below 35 latitude you most likely will want fans2) Age/Build of the House, i.e. is it going to be a hassle to get a box installed.

Main reason was the building age.