You're doing all the right things, IMO and you're far ahead of myself at that age.

Comparable number of bedrooms, baths, square footage, neighborhood, age of property, etc.  

It's most likely not high enough given the age of the property.

Hi Charlie, In this age of financial technology advancement, a checkbook control IRA is no longer the only option to cut multiple checks from your IRA economically. 

You register for a Commercial Activity License, which is Philadelphia-specific, and that number allows you to apply for a Rental License.I'd encourage you to look into the rental regulations in Philly because you generally also need a Rental Suitability Certificate, and you may also need a Lead Safe Certificate if renting to children under the age of 7, and you want to make sure that your duplex is legally zoned for 2 units and for the commercial use that you're planning.

My day job is as a mechanical engineer, which I love, but don't intend on doing till retirement age.

You will certainly have a leg up on the competition when you get to be my age. 

Maybe my age makes me higher risk?

@Gabriel Krut great age to start while in college!

It's based on a lot of factors, such as amenities offered (i.e. fitness center, clubhouse, swimming pool, etc); costs to operate/maintain common areas (i.e. landscaping, electricity for common light fixtures, gates, repairs to roadways, parking lots, etc); cost of any insurance that's required; size and age of the property and infrastructure; planning for future capex projects for the property; etc.