However, I think from a financial perspective, it's likely a better idea to pay off the debt or add the money either to a taxable brokerage account or a retirement vehicle like an IRA.

The 'what you get' for the money factor is highly applicable from Brookings to Astoria and licensable STR coastal vacation rentals are still regularly attainable at workable terms, Luxury and oceanfront and lakefront properties tend to perform above the 10% of valuation in gross annual income for prime coastal STR's and as an example I've seen a $2.1 Million Oceanfront home produce $300k in gross annual income.

They both understate the amount and regularity of costs.

He is the mobile home flipping god for So Cal and he regularly speaks at RE meet ups.  

Retirement distributions are considered taxable income(Federal and state).You mentioned self-managing the rental properties so it may be that the income will offset against the rental loss.However, you will still be subject to the 10% penalty.Have a conversation with your CPA and ask them to draw you up a draft of several different situations and see if that is something you want to move forward with.

If he's a vet, I'm sure there are resources he has access to that others don't, in addition to the regular places for support (eg local church). 

I don't think I can ask the renters to irrigate the lawn regularly?

I'll send you my regular email.

If you have a regular PM, are you personally listed as the landlord or owner on the lease? 

Pay no taxes as its a non-taxable event.2.