How many Macs do you have that will be backing up;?
If it's only one, the fastest, most reliable, and cheapest solution would be to connect a USB hard drive directly to your Mac so Time Machine backups can occur automatically.
If more than one Mac will be backing up, then you will need a much more sophisticated.....and expensive....device called Network Attached Storage, or NAS for short.
The NAS connects to your Wi-Fi router with a permanent wired Ethernet cable connection, but Macs will be able to back up to the NAS over the Wi-Fi.
Synology would be the brand to look at. More info here: https://www.synology.com/en-us/support/nas_selector