My home router ASUS RTAC68U has support for dual-wan which means it can be configured to use a 3G/4G USB-modem as backup connection if it’s primary broadband connection dies. I had a Huawei E392 USB-modem, but it was broken, and the USB-modem seems to be out of stock (end of life maybe) everywhere so I started to search for an used on blocket.se where you can find used stuff.
I found what I was looking for. The 9th of december 2014 some one called Fredrik had advertised that he wanted to sell a Telia branded E392 for 500 SEK, and dropped the price to 400 SEK. This was on the 4th of january 2015 and I sent him an e-mail offering him 250 SEK including shipping for the modem if he still had it. I got a reply saying that he would agree on 300 SEK.
The 5th of january 2015 I did what you should not do. I pre-paid for the USB-modem, via bank transfer. I got an reply that money was on his bank account and that he would send the modem to me.
Today, the 8th of january 2015, I had a usb modem in my mailbox and now I am going to set up the dual-wan. Still, in 2015, you can trust people. A good feeling!