If you buy some now, you will get extra coin after the fork 
that's something to look for too 
that's something to look for too I've heard of ethereum fork, is it like bitcoin fork that produces bitcoin cash?
if so, would the extra coin of ethereum fork be a new coin?
Yes, it will be like that. Not sure what would be the name, and how it will all play out, but whoever has ethereum (I believe same rules as Bitcoin, you need to have at least 1) and a wallet that supports the next coin and you golden