Actually, this is exactly what BePro Listings does. Its a wordpress classifieds listings plugin which works with buddypress. Members can create and manage listings from their buddypress profile and their creations show up in the activity feed.
You can setup google maps, cost, and several other features 100% for free. beprosoftware.com/products/bepro-listings
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You are right about job board or marketplace type plugin’s being out of date and complicated to hack. BePro Listings is constantly being updated and has a plethora of wordpress hooks and filters for expansions. In fact, that’s how the plugins/addons all work together, because BePro Listings is so extendable. Its built to fit into any wordpress theme