Budget for Proprietary Search/ Cost Per Acquisition?

For those doing full or partial proprietary searches, what is a reasonable amount to set aside for marketing? Expenses like: mailers, cold callers, etc. Tried finding previous posts from brokers about cost per acquisition but couldn't find anything. Idea of putting ~10% of search budget towards marketing seems like it would be well worth it considering you'll likely get a much better deal than on market. I'm deriving my confidence from sourcing off market RE deals in the past and wanted to know how translatable it was/ hear from people who have went this route.