KKJS

You've probably found an answer elsewhere since, but in case anyone else comes by this post, maybe via google like I did, I will provide the answer.

There are two achievements for the game: Cleaning up everything and getting all the money.

So, all the paper money you find, dump that into the blue lock box that belongs to the janitor. Everything else goes into the incinerator.

Google cheap cd keys.

Really, unless you are keeping your eyes on a big sale on one of the big online stores, googling cd keys is easily the cheapest way to find a game.

Look at this list:

http://cdkeyprices.com/product/Saints-Row-4-CD-Key-Steam.html