But I'm also building an ADU here at our primary (nearing completion). 

The fha 100 mile rule will be triggered whenever you try to vacate your current primary and also trying to use the rental income to qualify.However, this 100 mile rule can be exempted for the following rulesRelocationIncrease in family sizeVacating a joint owned propertyNon-occupying co-borrowerIf you are not trying to use FHA on your 2nd househack, you can use conventional and the rules that I mentioned above will not be a concern.

Cash for keys is a good last resort, but not a good primary option. 

If it is your primary residence, you (and your partner if you have one ) are the only one servicing the debt.

I haven't gotten any replies yet, but your post offers a good starting point for what to consider as I decide to rent or sell my primary home when I move. 

I am planning to sell my primary residence I purchased on December 2020.

Her D-to-I is high due to the purchase of our primary home and with us starting to supplement her W2 income with 1099 income.

Is this a property that was used as a primary residence before converting it to a rental?

Most work this way Rates: 9% to 13% (Most Deals are 11-12%)Terms: up to 36 Months (Most Deals are 6-12 months)Fees: 2-4 points(%) of loan amount paid at closing (Most Deals are 3 points(%))Minimum Loan Amount: $50,000 (For loans less than $250,000 $2,500 minimum fee)Max Loan: 65%-70% of After Repair Value(ARV)100% Rehab Financing Available (Require 20% of purchase price down payment or cross-collateral)Closing Timeframe: 48 Hours - 3 Weeks (Most Deals are 2 Weeks)NO PRIMARY RESIDENCES, NON-OWNER OCCUPIED ONLY, BUSINESS AND COMMERCIAL USE ONLY.

And the funds cannot be used for anything that is considered to be, or is actually part of, your primary residence.