I plan on getting this set up for my dad but don't know what the requirements could be for such a thing. Probably will have 2 or 3 ip cams connected

Depends on what quality you are aiming for and what kind of encoding. A rasberry Pi could actually be enough. I'm not quite sure tho.

For 3x 1080p a pentium 3xxx minimum is recommended.
http://felenasoft.com/xeoma/en/help/calculator/

So something like a intel NUC

This version already has 2GB ram, a windows 10 key and 32GB storage from flash memory.
https://www.amazon.com/Intel-Canyon-BOXNUC5PGYH0AJR-Desktop-Graphics/dp/B015RA5DDQ/ref=sr_1_1?s=pc&ie=UTF8&qid=1478401244&sr=1-1&keywords=nuc%20pentium

You would be able to add a 2.5" HDD for more storage.
like a 250GB HDD would make you able to collect data from 2weeks 3x 1080p H.264 encode

This post was edited by ZwiX on Nov 5 2016 09:10pm

Actually a rasberry pi can handle up to 4 camera's with these settings:

h264, 1920x1080 resolution, 4 mbit/s bitrate