In the late 90s and early 2000s, back in the days before board games and tabletop role-playing games became popular and as widely-accepted as they are now, my buddies and I were huge gaming nerds. Warhammer 40K was one of our favorite hobbies, and I say hobby because it's more than just a game. It's something of a lifestyle in that it requires players to shell out hundreds of dollars for miniatures, paints, and accessories, spend hours painting them, and constructing terrain for tabletop battles. My friends and I would joke that it was almost like having an expensive drug habit, given all the money and time that we poured into the game, and how it often kept us up late into the night. Once we gave up the game sometime in college, many of us swore we'd never play again. It took up too much time, effort, and money and we thought we'd never really be able to play again. Most of us decided that we were never going back, and a lot of us sold off our armies.
Then a couple of years ago, Games Workshop released Kill Team--a tabletop war game set in the Warhammer 40K universe, with lightweight rules and quicker pacing for skirmish battles. Instead of fielding a 2000 point army (each miniature in your army is assigned a point value) like we did in our Warhammer days, my friends and I could now field a much smaller squad of 100 points, with somewhat more limited options. Games are limited to 4 turns and can be set up and played in a couple of hours. This all makes gaming easier, and much more manageable to the average player who is typically too busy to paint minis and assemble terrain, let alone actually play a game.
Still, there is a cost. It's not as costly as a full Warhammer 40K army, but I would still need to dedicate a few hundred dollars to a kill team, some paints, rulebooks, accessories, and some terrain for a proper kill zone (the game's play area, made up of modular terrain pieces). To make it easy to start playing the game, Games Workshop has released boxed sets for each type of kill team and special rules for the various minis and equipment that they can have. As well, there are some amazing supplementary products for this game--including some incredible miniature terrain for your armies to fight on. But making the initial investment isn't easy, especially when I might need a few other people to play with--and I wasn't quite sure that my friends would be into it.
To get around this problem, I started small. Lots of long-time 40K players have sold off their figures and upgraded to newer ones with newer editions coming out. I did a little shopping during convention season and grabbed a few squads of old space marines from the 90s. You don't even have to go to Adepticon or Gen Con to find used minis, though--they're available on eBay. I picked up some nicely-painted Space Wolves and Blood Angels at Adepticon for about $20-$30 each for enough used minis to field 2 kill teams. That's not a big investment, especially for pre-painted troops. After re-gluing a few arms and weapons and doing a few paint touch-ups, they were ready for combat (though they can still use some better basing). Note, that Space Marines have gotten bigger over the years--in the Warhammer 40K world, the've actually been genetically engineered to be larger, and the minis reflect this--but that's not going to stop my using some older figures to test out an army that I might to make a bigger investment in. Digging out my old Tyranid army gave me another squad of troops to try out. That gave me enough troops to get off the ground and kick the tires on the game before committing to an army box set and rules for the Kill Team that I'll want to play long-term, and maybe enter into some tournaments.
As for the rest of what you need, the rulebook will only run you about $30--which is reasonable.
The game requires mostly D6s and D10s. Most gamers already have those. You'll need a small tape measure, and perhaps some chits to keep track of certain conditions that may apply to your minis. Most of those are easily attainable. You'll also need some terrain to get things going. Using random household objects for your first game to try out the rules might be a good way to go if you don't have the time to invest in making terrain. If you play roleplaying games like Dungeons and Dragons, you might have some scenery around that you can turn into something that will provide reasonable cover in a futuristic battlefield. If you're ready to get into building terrain, however, a $10-$15 sheet of foam insulation and some inexpensive acrylic paints will get you started. Just find one of the many online tutorials that will show you how to sculpt it into realistic looking miniature rocks, mountains, and structures.
If you're lucky enough to have access to a 3D printer, you can really make some awesome terrain at little cost. Thingiverse.com has a ton printable files for free that you can use to print out everything from cathedral ruins to that cool floor grating that seems to cover every inch of the Forge Worlds in the Warhammer universe. Though it will take you some time, you can print out some nice scenery at low cost--but not quite as nice as the pre-made Games Workshop sets.
If you've been thinking about maybe trying out Warhammer 40K, and weren't quite ready to take the plunge, it may not be quite as big of an investment as you think. I knew that it required a lot of investment when I started looking into Kill Team, but taking it slow, buying the core rules, and a few used minis (since I knew I didn't have time to assemble and paint them) was a big help. Once I was hooked, 3D printing some buildings on my Ender 3D printer and making some foam terrain weren't hard as weekend projects. It was surprsingly easy to get into the game, and if you're reading this while on lockdown during the Covid-19 epidemic, you might just have the extra time on your hands to take the plunge.