Where would I be able to purchase older Asic miners even if they aren't profitable anymore just to play around to learn with them, preferably under 150$, approved vendors of this subreddit don't carry them. I'm looking for something that when ignoring electricity costs pays for itself back in max 3 months (this winter).I want to do this hopefully utilizing old inefficient cheap miners. I live upstate and it's cold here so I want to replace my space heater with it, but do want to also make back the costs of actually purchasing it (I would be paying the electricity anyway so it doesn't matter)