I can't connect you with IRA/401k lenders, but certainly you can educate folks on this concept.

Also, focus on 2 years of job/income stability.Class D Properties:Cashflow vs Appreciation: Typically, all cashflow with little, maybe even negative, relative rent & value appreciationVacancy Est: 20%+ should be used to cover nonpayment, evictions & damages.Tenant Pool: majority will have FICO scores under 560 (almost 30% probability of default), little to no good tradelines, lots of collections & chargeoffs, recent evictions.

In fact, I recently used one of the methods from the book—where Chris Voss talks about "going negative" to soften the blow of an offer and make it more palatable.

Great assets (cashflow and appreciation, low to no cap ex), steady (low cash flow, good tenants, slow appreciation, low to no cape ex, and dawgs (low to negative cash flow, lots of cap ex coming, aggravating tenants).

But need a little more clarity on the "all in one" concept. 

I love this concept!

You never know when interest rates will go negative.  

If you have positive cash flow, and  you use your own cash to pay off the property, you are adding to your cost.If you have negative cash flow, the negative comes out of your pocket and adds to your cost.If you try to change negative CF to positive by adding to the down payment, thinking the lower mortgage payment will change the negative to positive CF, you are only paying the negative CF upfront,...and still adding to your cost of the property.Profit starts AFTER you have recovered your cost (cash) in the form you paid for it (cash flow). 

To do it safely its a niche and one needs to be aware of all the things that can trap you and cause you a negative experience..

This creates a negative initial position.