Hi Priscilla,
I haven't read the book you're talking about but have attended a meetup with someone who does cost segregation studies and, from my understanding, you need to have a certain amount upside from a tax perspective for the study to be worth it. I believe it costs a few thousand dollars to have a professional complete this for you. Not sure if it is worthwhile on a single family rental/BRRRR (unless you plan on purchasing a multi-unit) but am very interested to hear how it goes for you. Please post an update when you're further along in your journey!
As a side-note, I live in Reno and invest out-of-state; my partner and I recently purchased a 6-unit and a cost segregation study isn't worth it based on the financials of this deal. So it may be case-by-case that the strategy works for you. It looks like you own and run a separate business too, so perhaps you're looking for tax breaks to help with that side of your life. I can't speak to that of course but again wish you the best of luck!
Regarding LLCs, I agree with Greg's response on your other post about this. Not necessary to get started and if you end up deciding you need one, they are very easy to set up quickly. I can recommend a local RE lawyer if you don't already have one, just shoot me a message.
Cheers,
Alex