This is going to be quite a long post. I might be going too in depth here for your brothers requirements, so please bear with me!
How seriously does he want to get into video editing?
If you going to use Adobe Premiere then make sure you have LOTS of RAM - especially if he's gonna be working with DSLR footage. RAM can be picked up for a few hundred Rand. 4GB an absolute minimum, but try aim for 8GB at least. A rule of thumb is that you can never have too much RAM. Video editing software stores the decompressed video frames in RAM.
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First, some background on how video editing software handles compression...
DSLR footage uses the common H.264 codec (MP4), and this requires the CPU to do a lot of decompressing when scrubbing through or even just playing back footage, as H.264 codecs use what is known as "Long-GOP" compression. Long-GOP stands for Long Group of Pictures.
Long-GOP works by only encoding or compressing certain frames individually (say 1 in every 15 frames). These 1 in every 15 frames or 'key' frames are known as I-frames. To get the rest of the frames in-between the I-frames compressed, the codec only records the changes in the image from one frame to the next, rather than the image as a whole, and the area's of the frame that don't change are discarded.
This allows the codec to squeeze video content into a much smaller file size than if every frame was compressed individually. This is great for getting nice small file sizes, but the BIG downside to long-GOP compression is that it is much more processor intensive than dedicated intra-frame video codecs - especially with video editing software! This is because every time you scrub or play back footage, the processor has to take the information from the I-frame or 'key' frame and rebuild all the frames in between. It has to do this every time you move through footage. This isn't much of a problem on systems with lots of horsepower, but it can be a problem on slower systems.
Many video editors would first convert their Long-GOP footage into a codec that uses what is known as Intra-frame compression. Intra-frame codecs compress each frame independently without interpolating the frames in between. This means that when you scrub on your timeline, the CPU only has to decompress the frame the marker is on and not the 15 odd frames in between.
This means that the video is far less CPU intensive, and you can scrub an edit without any lag from the video editing software. The downside to I-Frame encoded footage, is that file sizes tend to be quite large.
All H.264 or MP4's use Long-GOP compression - hence why you would need a higher spec'd machine to edit DSLR or AVCHD footage.
An i3 will probably be a bit under powered for serious video editing, but this all depends on how much editing your brother plans to do.
If he can't afford a faster laptop or PC, then there is an alliterative solution to edit HD video fairly effortlessly! He'll have to convert the footage to an intermediate (I-Frame) codec. This will allow him to edit on even the low end scale of CPU's out there. The drawback is that all the footage would have to be converted first, and depending on how much footage there is, this could take hours.
Dunno if this helps :/
