Product qualified leads are contacts who've used your product and taken actions that indicate interest in becoming a paying customer. PQLs typically exist for companies who offer a product trial or a free or limited version of their product (like HubSpot!) with options to upgrade, which is where your sales team comes in. An example of a PQL is a customer who uses your free version but engages or asks about features that are only available upon payment.
BoomTown is missing a lower-cost option for smaller agencies and individual agents. Even though their lead generation marketing efforts and CRM combine the best use of communication and technology to produce a great product that stands out among real estate lead generation companies, BoldLeads or Real Geeks might be a better choice if budget is an issue.