Internet and hardware are the main drivers. Electricity is the maintenance part of the bill.

Depending on what you want to host, an adequate server is important. And depending on how many clients you want to satisfy, you need a good uplink and a serviceable downlink.

I use a FriendlyElec NanoPi R6s at home that is connected via VPN to a 5 bucks VPS, acting as a frontend and workaround for my dynamic IP - most non-business internet providers don't provide a static IP, so you might have to dig into that hole too.

In total; What you want to run denotes the hardware you need and the speeds your internet must provide.