Use it as heaters is a great idea. I thought about it too, however I looked at s9 models I can buy for around $50 on local market.
I really appreciate your intention to get clean sats. But maybe you'll read @DarthCoin tutors how to unKYC sats and you'll end up with 5 million in the wallet instead of two noisy heaters?

Main purpose is progressive accumulation without having to do p2p all the time (DCA)

Second purpose is to use as heater

I have access to low-cost energy

jp305

Today with $3k you can become an owner of 5 million sats. I'm not sure you'll even mine back 5 million sats with these miners.

If just want to try what mining is maybe just start with nerdminer?

bitcoin_Mining

Is it safe to buy used miners?

What the purpose of mining?
Today with $3k you can become an owner of 5 million sats. I'm not sure you'll even mine back 5 million sats with these miners.
If just want to try what mining is maybe just start with nerdminer?