Expect a custom ADU to take 9–18 months, with 3–6 months for design and permitting and 6–12 months for construction, depending on complexity and contractor availability, and the speed of processing permits.

Reaching out to a loan broker or two could be pretty beneficial too.

Yes I did one myself and broker these products all the time.

Hi Dean - we had access to a DSCR product until a couple weeks ago - it's currently paused, per my conversation with one of the loan brokers I work with. 

I'm a broker and property manager.

Quote from @Brandon Croucier: Hey Bruce,I recommend working with an experienced DSCR Broker who knows the ins and outs of the industry to guide you in to the right product and pricing for you. 

I have family in Houston, Dallas, and the Valley, I was networking with brokers in San Antonio, but the Taxes seem to be quite high as well in that State, although much favorable laws/regs on the landlord side.

I still think developing good relationships with brokers is the best way and will get you the best results quicker than going direct to seller. 

In Ohio we just consider wholesaling brokering real estate.

I'd look for mortgage brokers in Canada.