You could buy a bunch of GPUs I guess. Take a look at
https://whattomine.com/ and see it for yourself. Assuming your electricity cost is 0 I guess anything could be profitable. But your apartment manager will definitely find out. Don't know how much they'll charge you, but I don't think it is worth the risk. Staking might be better imo.
Thx for mentioning this site. I will take a look at it! Yeah, any setup would be kinda profitable, but I also don't want to waste money in not effcient hardware.
Yes, I thought about that. I am aware that they will find out if too many people in one building start to mine. But right now I would be the first one in my building (as far as I know) and also with 90 units in one building I don't think it will stand out between the electrical stoves, fan heaters and dish washers etc. At least not with a setup for 1000€.