No it's not permanent. When you take the corset off, everything gets back in a normal position, and you can't permanently reshape the waist by wearing the corsets.
Also the lower ribs (for most people) are very flexible so they can bend without breaking while tight laced.
When you are tight laced in a corset, inner organs do change their place, but they return to the normal position after removing the corset. But it is important to start with a small reductions. The organs move the similar way like in pregnancy so it's not dangerous cause woman body is naturally predisposed for it.
Of course all of this also depends on a humans anatomy and constitution , so some people can get a huge reduction, and some people don't. I'm lucky to have an anatomy of those who can Also the main part is on the corset shape.
I still need to finish lots of things before putting my first listings. Like measure form, standard sizes, possible mock ups, postage charges... Now I can say only that the prices will be low until I got some feedback If you are interested I can let you know when I start.