If you can't keep control of your personal finances, you are highly unlikely to succeed in real estate investing.

If you haven't already, consider looking into whether or not your fiancé would have been covered under the Servicemember's Civil Relief Act (SCRA) https://www.dmdc.osd.mil/appj/scra/In certain instances, things like high interest credit cards and certain loans would be capped at 6% APR, with any overages/fees being FORGIVEN and not just deferred. 

I work with the top mortgage broker in the country and offer over 140 lenders in 44 states.

This is a core deal, which certainly offers some risk mitigation, as they allude to.  

Owners mistakenly ASSUME all PMCs offer the exact SAME SERVICES and PERFORM those services EXACTLY THE SAME WAY, so price is the only differentiator.So, the first question they usually ask a PMC is about fees - instead of asking about services and HOW those services are executed.EXAMPLE: PMC states they will handle tenant screening – what does that specifically mean?

I offer this exact deal in my markets. 

So it can be done if you really have tight subs and can push them to start each phase as soon as the previous one ends.There are some other tricks we've learned to improve quality and turnaround as well - prefinished siding and tongue and groove. 

I'm going to sell one of my rental properties and offer seller financing with a 30-year mortgage term.

Agree on above - holding very high interest (presumably) CC debt should be first priority to pay off before buying the first investment property

You can still save on rent doing house hack if the basement is high enough to bring another unit.