I have read I will need to use a third party service to make this happen.  

America is full of quiet & desperate strugglers; you wake up one day and see someone or something failed.

Quote from @Robert Briggs: Going to sell one of my rentals (Houston Area)  and need to finance 30-40k and repay the rehab/ make ready loan after sale. 3-4 months .

My pre conceived notion was that 80 was sufficient @Tyler Garza With respect to DSCR loans, the LTV is only one factor that lenders consider when underwriting a loan.

You would then have two loans, one on your home and one on the refi to access the equity on the investment home.Why not just use the refi cash out from your home loan for future deals? 

I also have no W2 and possibly one of the highest debt to income ratios in the country.

If I were to invest into one that was grandfathered in, would I have to convert it to a MTR?

I recently completed one on a multifamily property and found it to be a cost-effective approach.That said, there are a couple of additional factors to consider beyond the code differences between a garage conversion and new construction:Coastal Overlay Zones – If your property is in a coastal overlay, building a ground-up ADU may require Coastal Commission review, which can add time and complexity to the process.

I did overlook this one.

I'm assuming you have one lease covering both tenants and not individual leases.