BUT I have also heard that it could trigger a due on sales clause, bringing the note fully due at any moment.

I know there are hundreds (thousands probably) of lenders out there that offer a DSCR product.

As you know its near impossible to find a good cash flowing deal in CA due to sale price, taxes and lack of inventory.Last one I closed on was over off of Germantown Road it was a great 2 unit that needed a little TLC for $160K but passed an inspection and was livable.

We have a 30Y Fixed DSCR product that would likely fit your needs. 

Great product but can be pricey monthly

For walls in common areas like halls and stairs, there are rigid products that can absorb some sound.

I wonder why they don't make roofline sprinklers or some other product like that. 

Most investors make the same rookie mistake: They focus on problems instead of people.
Telling sellers everything wrong with their house and justifying your offer with repair costs doesn’t build trust—it kills it.
...

Small shop brokers that have access to multiple programs so that they aren't beholden to one or just a few loan programs will typically get the most competitive product for the borrower. 

Book recommendation #1: Hands Off Investor by @Brian Burke https://store.biggerpockets.com/products/the-hands-off-inves...Book recommendation #2: Lend to Live https://store.biggerpockets.com/products/lend-to-livePodcast Recommendation: PassivePockets podcast is focused on passive investing in syndications - https://passivepockets.com/podcast/Passive investing summit: PassivePockets Summit May 2-3rd in Columbus https://get.biggerpockets.com/passivepocketsevent/I make these recommendations specifically since you mentioned passive real estate investing, and syndications or hard money lending are really the two most passive ways to invest in real estate.