I don't know what your past construction experience is (or if you're handy at all) but if it's minimal, then I would stick to rehabs first (doing cosmetic renos, then more complicated as you aquire and rehab) then go into new construction. 

But since my spouse and I have the same debt other that student loans, which is minimal, our monthly debt pretty much stays the same, but our monthly income doubles almost.

Rather, I'm trying to maximize the new tax laws (bonus depreciation) to minimize my tax liabilities in the day job. 

You can minimize the down payment by living in the investment property, utilizing your skills to build value, then rolling your equity into your next investment.Monthly debt vs. monthly obligation is your DTI.

there can be agreements to remedy some of the down side but if the middle man or the end user goes dark this is a tough spot to be in for the original seller..

Our professions are not related to real state or construction, and I never had to constitute any kind of company in the USA (did back in Spain, but laws have nothing similar).After much reading, the only two things I'm starting to get clear are: that buying and selling within a year has very different tax implications than living in your home for a few years then selling it, and that I should find at least a good CPA and possibly a good lawyer specialized in real state to figure out how to structure this to minimize taxes and liabilities.At the end of the day, my goal remains the same that I want to end up with a couple of investment properties, don't necessarily need to base my retirement on that, but just to not have all my eggs in the same basket.

How can I create a tax structure that minimizes tax burden as a SEI?

That's a great tip, expect a minimal 90 days grace period to receive funds from borrower.

My partner and I were able to close on a duplex for $33k with minimal repairs expected, but still anticipating $8k - $10k to be spent over the coming months.  

Since this will be my first investment, I want to minimize as much risk as possible.