First time buyer of video surveillance - recommendations?

Hi

I live in a house in Northern Europe and need some outdoors video surveillance. I need two cameras that will be placed under the overhanging eave, on two sides of the house.

I'm looking for something that runs on batteries - if this option is high enough quality - and something that's water resistant / can handle our cold climate.

I think we're looking for an NVR as we have a mediaserver at home. I would love something that can record eg a weeks worth of footage on our network storage. As SD card is also an option but I'd prefer not to, due to theft of the camera and video evidence. I'd like to avoid any cloud based solutions as they tend to come with a monthly subscription fee. I'd rather pay a bit more up front than have a monthly expense.

Any suggestions / corrections / advice for this? I'm a first time buyer and don't know a whole lot. Thanks in advance.