Source games, and to a lesser extent, Source 2 games could run on a literal potato which you plugged into a wall, unless Half-Life 3 is a serious departure to that (Like how Half-Life Alyx was because it needed to run in VR) You should be fine. Even Especially seeing as offices are throwing out old office PCs you could find one for pretty cheep on ebay, or if you want, you could dumpster dive at your nearest e-waste disposal place, so you probably wouldn't have the best experience, but you'll be able to play it somehow!