When I got back into 40K a bit, I built a pair of Oldhammer (2e) armies for maybe a couple hundred USD on ebay. Just be patient and wait for stuff. Theres always guys unloading their stuff because they got tired of it / reddit told them chaos is 1% less optimised this edition / they got laid.
But also just play literally anything else
You can get a game of Chain of Command going in 15mm for something like 40 USD per player.
If you MUST play 40K and MUST have pristine stuff, Kill Team and the Combat Patrol stuff is quite affordable.
But also just play literally anything else

If you MUST play 40K and MUST have pristine stuff, Kill Team and the Combat Patrol stuff is quite affordable.