This is counter-intuitive to my goal - slow and steady save to purchase our first investment property (with more to follow). 

There are lenders who will let you pull out 75%-80% or so, possibly based on rents vs your own income if you don’t qualify that way, but their rates and fees will typically be higher than conventional loan products, and you may need rental history to go that route.

Yes, there are other asset-based loan products besides DSCR.

Due to item 1, adding an ADU can require years to start achieving any return (once the accumulated cash flow recovers the initial negative position).4) Adding an ADU is a slow process.

You simply will not find that product. 

There's certainly quite a few of us around but things have been kinda slow since the interest rates jumped up and BP is doing a revamp of their website and overhauling the different premium tier packages and I've noticed its been messing with notifications and keywords and such so some people are just missing posts they would normally see. 

What kind of loan product should I go for?

A newer house with a mortgage will take longer to build up equity, which could slow your growth as an investor.5.

**Local Credit Unions & Regional Banks**: Many local financial institutions in South Carolina offer investor-friendly loan products and might be more flexible with terms for a cash-out refi.

Do you need income now, or is slow appreciation ok?