So in conclusion, it would be financed as a conventional with 20% down ($100k), and out of the $400k, $300k will be at 3% and the remaining $100k will be at the current mortgage rate?

Your plan A of recommending a 3rd party servicer remains sound.

The 401k I used to have said if I default it didn't negatively affect my credit, but that it would become a taxable event like a withdrawal (come tax season) and I would have to pay penalties for the amount I had remaining. 

We do not suspect foul play because apparently that tenant's relatives have reported to the remaining tenants that the MIA tenant has moved in with another relative (but did not give that MIA tenant's new contact information). 

The key to finding good deals is to remain open to alternative investment strategies and consider all potential deal sources.

Since the value of the property should remain static at best and might actually decrease over the time involved and the highest bid amount probably would not increase, any overage going to the OP will decrease. 

The remaining heirs don't have enough information to complete the remaining Affidavit of Heirships.

Properties in New Orleans often remain on the market for more than thirty to sixty days for a variety of reasons, some of which make the market distinct.

There are a couple of platforms and several hard money loan funds that have lower default rates.3) loan to value: they are one of the few remaining platforms that still has loans that are under 65% LTV.

Economists:It is said that there are 4 phases of a real estate cycle: (1) RECESSION (supply greatly exceeds demand and high vacancy rate); (2) RECOVERY (rental growth remains stagnant with little signs of new construction but the economy feels like it is headed in right direction); (3) EXPANSION (job growth is strong and increased demand for housing.