Permissions to a document library

So I'm not sure how to do permissions or best practice for my situation. So I work for a real estate company and when they buy a property they have documents for each stage of the project. Stages are as follows: Due Diligence -> Purchasing -> Management Some people will only need access to the due diligence and some just need access to purchasing, and others to only management. So reading up on this it looks like I might go the way of making three different document libraries, and then basing permission on those libraries, however documents will have to be moved from one library to the next as it progresses through the property purchase stage. Is there a way to base permission off metadata tags or content type on the documents, and just use one document library?