But my experience over the last 10 years of building new homes is that NOTHING comes down might stay the same but will rise almost annually Like Cement always goes up in Jan. 

Is anyone investing in texas (in long-term rentals) that knows about this and has experience with this?

It's not some MLM, pyramid type gig you can just experiment with attempting to make quick or easy money.

I am an seasoned real estate agent and affordable housing compliance manager in NYC with some experience in the Hudson Valley Area.

There's a lot of pitfalls there that you're probably not going to be aware of without experience. 

But even then, seller financing is rarely substantially better than another investment they could make (including trust deed lending, which will often be at a higher rate than seller financing)In my experience, the owners who find owner financing advantageous are at the ends of their careers and are not interested in looking for another investment (other than the usual retirement funding sorts.)

Does anyone have any experience (or know someone or a company that might) be able to demo a concrete staircase Ana turn it into a driveway and ADU ramp ?

Consider starting small, like with a duplex, to get experience.

If you’re open to learning more, I’m happy to share resources or insights from my own investing experience there.

Most times, the top of a brokers list are those with experience who they've worked with in the past.