Currently I've been working on trying to get my active income up, because I have no other source of income than the duplex cashflow ($1100/mo).

lets look at renting and refinancing options 

Hey BP Family, I'd love your insight on this.I'm currently weighing two intriguing options: house-hacking a 4-plex or venturing into the realm of MTR with a single-family home or duplex, particularly for renting to travel nurses.

I too am looking at Detroit as an OOS option and would love to see your neighborhood info.

Get the cost analysis and blue prints done and work it out with the construction loan committee and start the work draw phase.The other options which can be a little easier is buy a home that will pass an Inspection/appraisal and not be "Subject to" but does need a lot of TLC/renovations and do it yourself.

So I have a non-primary house that is valued at $220k on Zillow (just a reference point), what options do I have to finance around 100k out of it to renovate the house?

Sharing an article I published here on BiggerPockets last year related to this topic on all about the financing options / qualifications / underwriting for STR income in case it helps you!

Either way, I'm glad it's being more recognized as a good housing option. 

Sourcing: whether agent, wholesaler, flipper, etc. many only have a vested interest in a transaction.

Not saying it's not possible or profitable in the rest of the city, simply the multi unit option and 0% vacancy from the university makes it a great option.