Is this spam? At any rate, you want to buy all four? Those four servers together are 7U, so a 42U rack would be overkill, unless you want to buy 4 or 5 of each of these four models or several JBODs. If you want to make money with your hardware, you need several commercial symmetric fibre internet connections, a local fibre-based network with (at the very least) 25GbE (SFP28), the relevant switches, and super-fast storage, i.e. not SATA HDDs. You also need heat management & cooling, noise insulation, i.e. a dedicated space, plus redundant power supply, and I’m not talking UPS, but something like a couple of diesel generators plus a large photovoltaic setup including battery storage. You also need to employ a couple of technicians and IT specialists, because I doubt you’d be able to handle all of this all by yourself.
And yet, even then you won’t be able to compete with the big boys in the field. They are renting out server/computing/storage space at scale, all over the world, and you would never be able to match their prices.
The best approach is probably to buy a small amount of gear and start learning, and then offer your services to businesses in your town, to set up servers for them and manage them for your clients. As a side-business using your own gear, you could then maybe offer storage space for your clients, so they can back up their own server or client machines onto your storage as a remote backup, and then you could scale up step by step. But you’d also need a cross-platform software solution that you can deploy for these kind of use cases, so you need software developers, programmers, a support team etc. (And still, I doubt you’d be able to match any of the big boy prices.)
Another way to make money just using your own hardware/storage, but possibly a risky one, is to run a full Filecoin node: https://spec.filecoin.io/ … you allocate your storage to the Filecoin network, and earn some of their coin in the process.
Similarly—if you want to avoid coins, which you definitely should—, you can run a Lightning node for the Layer-2 Bitcoin payment network, or a Cashu mint (or a similar federated mint). But this you can do with a cheap Mini-PC… you don’t need a homelab for that. But you’ll need lots of liquidity and payment channels for your node if you want to earn sats by routing transfers.