eBay is the place to go. Often you’ll see brands like HP, Dell, etc. They are most likely to be re-branded LSI raid cards. Adaptec is an alternative to LSI, I’m using both, in different servers, and they are both good.
Some cards come with batteries. If they are dead they’re expensive to replace. For homelab use, I wouldn’t be too bothered with them. For production servers, it’s more important.
If you want to use ZFS you’ll need a flash the card or buy one where it’s already been done. Expect to pay more for pre flashed cards.
I’m in the UK and prices are different here to the USA. I’ve paid as little a £5 and as much a £40 for used cards. Just depends on how urgent your purchase is.
In the UK you can buy ex-corporate SAS drives is batches of 10 and sometimes 20. Search on eBay Auction for: 10x SAS. Depends on the binding as to how much you’ll pay, but I’ve paid as little as £36 for 10x 2TB SAS drives and as much £62 for the same. The larger the disk capacity the higher the price.
I’ve found that used cards and SAS drives to be good enough for homelab use, rarely had any issues. Would I use them on a production server? No.
Also a long time homelabber, with a lab that’s run on a tight budget. There’s no money for the latest and greatest, but today’s white hot tech quickly falls out of favour and sooner or later finds it’s way to the bargain basement. That’s where it’ll be.
It’s at this point I’ll be retiring older tech for newer old tech and so it goes on. Incremental upgrades, never finished.
On the whole, hardware wise, I’m very pleased with what I’ve got and don’t feel I’m missing out, but that won’t stop me looking for the next best thing my empty pockets can afford.