A lead is not a list. A list is a set of names bought by the row, with no enquiry behind any of them. A lead exists because one person filled in a form about a loan they want, and the difference shows up in the first thirty seconds of the call.
What a lead is worth depends on what was checked before it was sent. Some suppliers check nothing beyond the form. Ours are phone verified by SMS, checked for duplicates, screened on finance and sold to one broker only. Lead types run from a plain refinance to a fixed rate expiry lead. The full breakdown of what sits inside a record is on the exclusive mortgage leads and qualified mortgage leads pages, and the three places leads come from are covered under how to get leads for mortgages.