TP-Link TL-WR700N Wifi Router for $10 with free shipping.
Normally $22 to $28.
A cheap wifi router like this will have limited range, features, and a limited number of devices it can support.
So, we would not recommend this as a home router.
It may be best when used as an "access point" or "bridge."
To use an an "access point", run an Ethernet cable from your main router (or Switch) to somewhere in your home that has a weak Wifi signal, plug it into this device, configure as in AP mode, disable DHCP, and set up WPA2 Wifi encryption.
To use as a bridge, plug its Ethernet cable into a computer or device that does not have built-in Wifi, and configure the TP-Link to connect wirelessly to your main Wifi router.