This is a very important point. Buy one thing (Combat Patrol or Kill Team) and then try painting it. In case you discover that you actually hate painting and want to bail. Even so, the gray Combat Patrol or Kill Team will be sufficient to play their corresponding game with. You can simply refer to Wahapedia for rules and faction data without having to buy books or search for PDFs.
I think this excellent advice. I absolutely hated building models, removing mold lines and gluing them together, but i loved the painting aspect. I liked the painting more than playing the actual game. I think buying a Kill Team is a very good entry point for a total newbie in the hobby. Also don't fall for the GW meme regarding tools and brushes, you get more bang for you buck if you just buy non-brand hobby stuff. I went through a ton of brushes before i eventually got around to buying a Kolinsky Windsor 7 series brush in size 1 and i never looked back, the hype is real and it is worth every single cent you have to spend on it. For colors Vallejo > Citadel for me, especially their paint range that mimics the Citadel range from when 2nd Ed. 40k was out, it's a perfect copy of those paints. Also cheaper than citadel, plus dropper bottles > paint pot. Build your own wet palette, no need to spring for overpriced branded stuff, there are a ton of tutorials on YT on how to build one with cheap household materials.
This is the last model i ever painted and by far my best work, it was all done with the previously mentioned Windsor Series 7 Size 1 (and Vallejo colors, their basecoat green is pure magic, that is just one coat on that mini, over grey primer) , the point in that brush is so good you really don't need to buy meme sizes like 000.

Just work on your brush control and always take good care of your brush, get a bar of brush soap (i bought curd soap from a drugstore, costs a fraction of what brush soap in a hobby store costs and is the exact same thing) to go with it and you will practically be set for life. You should of course get a bigger brush or rather a good-quality airbrush if you start painting vehicles and bigger stuff.
Edit: While it may look like a Salamander or Dark Angel it was supposed to be a Blood Angels My Dudes

successor chapter. Here's some paint schemes i wanted to incorporate for troops.
The yellow is actually supposed to be a bright and saturated gold tone. Planned to do Sanguinary Guard in bone and Death Company in white. Ambitious project i never got around to come close to really work on. Even looked into making my own decals back before 3D printing took off.