As a GC I can advise try to retain control of your finishing material orders (anything where you need to make a choice ((tile, flooring, lites, faucets, tubs)) vs. construction materials (2x4s, mortar, shingles)) because we get those discounts on the finishing items and we keep them!

Going with a S&P 500 fund can be a safe easy choice.

I am wondering if everything in the Ultimate Beginner's Guide and other real estate books for beginners that were written a decade or more ago still completely apply to nowadays investing.

Ultimately, adopting an investor mindset means being proactive, staying informed, and continuously seeking knowledge to make informed decisions.

This will make it harder to afford, harder to get lending, and ultimately limit the buyer pool which puts negative pressure on prices.  

You have a choice to get 100% (or 50% equity) before crash, or hold it long term.

I think ultimately, thats the key. 

Turnkey properties can be a solid choice if you're looking for a low-hassle way to get into short-term rentals, especially if you’re new to investing or don’t want to deal with renovations.

He is the ultimate sales guy. 

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.