Cheapest good option is a used Intel/Asus NUC.

Have an Umbrel Home and it’s reasonably priced however the two big flaws are an underpowered CPU and Umbrel still has not enabled GUI backups. You have to CLI into each app individually to back them up, which practically means most people never will.

Start9 Server One is modestly higher prices but has a MUCH more powerful CPU, and is worth the price imo, but people will have varying needs and usage to think about specs vs usage and price.