Two routers, how to make friends?

Question

WiFi

There are two Internet connections, in two apartments, to two different providers, PPPOE connection. Two different Wi-Fi networks.
Which router with which technology should be installed so that if my provider has problems with the Internet, the router automatically connects to another Wi-FI network and receives traffic from another provider?
Physically, there is no way to connect the routers with a cable.
Now in one apartment DIR-320 in another DIR-615

Answer 1

A router with the ability to reserve an Internet channel, that is, with the Multi-WAN function. Plus, it has a Wi-Fi bridge to connect to a neighbor if the router itself does not allow this.
Бюджет примерно 8000 руб.