I once quit CS because of steam, but now I figure out with the old and in with the new

I've never written a plugin that involves a vault so im trying to work it out. I checked the functions list for files and im kinda confused. I have a file called bank.ini and I want have it write the users money in it.
I want it to write to the file in this format:
Steamid money
It will be updated every round. When a person comes back the the server it will find his id and put his money back the way it was when he left the server. If anyone can write me an example to get me started I would very much appreciate it. (this is for CS)
-Knekter
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