Can I render the first half of an animation on my computer and the second half on my friends the make them video files and combine them?
Render as image sequence on each computer, then encode those frames as a video file later.
open the project on both computers and just change the range of frames each computer should render.
Never render to video for two reasons:
If the computer crashes you will loose all, if you render as separate images you just loose the last rendered frame.
The second reason is that by having an image sequence you can then find the correct encoding settings without having to start from scratch.
Also, if you render on different computers as video then you have to re-encode to make the files a single video. Every time you encode you loose quality