In this strategy, it's important to note that appraisers do not consider the ADUs to be actual Dwelling Units so an SFR with an ADU is not the same as a Duplex, even if all of the features (bed/bath, GLA, etc are exactly the same).

Purchase price: $242,548 Airline Crash Pad with 18 beds available for a total potential for $4225 per month.

After sitting on the sidelines trying to get into real estate investing for several years, I have the opportunity to purchase a 1 bed, 1.5 bath home in a desirable part of the California desert.The purchase price is $299,000 with a 7.3% interest rate and 3% down.

Market rate right now is minimum 300 dollars above what I am charging for the unit but my tenants are good and I don’t feel right springing such an increase on them. 1500 per month is what I would have to pay for a 2 bed 1 bath apartment around here and my unit currently is 3 bed 2 bath. 

1300sqft 4 bed/2 bath SFH versus 1300sqft 2/1, 2/1 duplex.assuming same area, both new builds, same finishes etc etc. 

We are planning to move out and will leave the washer/dryer,side-by side refrigerator, sofa, entertainment center, beds, microwave, etc.

That may help cover your current mortgage payment, the HELOC and still put cash in your pocket.Last ditch: if you happen to have somewhere else to live: If your "Investment home" is close or near to an airport (10-15 mins) consider: Renting Beds to Flight Attendants. 

Property: SFR in Ontario, CaliforniaRent $3200Mortgage Payment (2.875% rate) - $2661.06 + $185 HOA = $2846Mortgage Balance - $456k Estimated Value - $700k(3 bed/2 bath)

What can we do, I am currently in a contract with this property, it is originally a single-family home and the owner added (3) 1 bed 1bath units at the back (without securing permits).

Anything to highlight to local area.Take another look at your beds.