Referrals are the best leads and the hardest to schedule. Running your own campaign means ads, a landing page, phone verification and follow up, which is a second job. A campaign run for you replaces that with a fixed cost per lead, agreed up front, with no retainer and no lock in.
Whichever route, the lead that costs a buyers agent most is the one that cannot complete. Half of one group we measured failed on finance, which is why we screen before delivery. What the record should contain is on the page about buyers agent lead generation, and the owner occupier version is under home buyer leads.