And my feeling is for MOST people Solo 401k is sufficient to meet their needs, and an actuary creating a custom plan is “overkill”.  

I think if you can write a solid letter of explanation stating that you are going to commute to Colorado from Washington for 4-5 months out of the year for your job (and why), that should be sufficient enough to run this as a primary residence. 

I hope you have verified that there will be sufficient equity and that you'll be able to qualify (either DSCR or Conv) for a takeout loan or cashout refi for the hard money.

While a detailed log is often sufficient, adding additional documentation can strengthen your record. 

But, something to add that you have to understand is that a 3-4 unit has to be meet the FHA self sufficiency test.

I need to ensure that the rent-to price ratio will sufficiently cash flow as I intend to hold at least 5-years before acquiring any other real estate.  

That might sound good, but keep in mind that quantity doesn’t always equal quality.

She may be getting alimony payments sufficient to allow her to qualify on her own.

Not sufficient for individuals' identification always, though.

Instead he/she claims that his/her invoice is sufficient.