Steve
Offer a free room to test your services. They are busy people and need reliablity and performance first time. Ive found a visit also works well offering again the free room.
Some letting agents will happily pay your fee for the above but some are real price shoppers and those you want to avoid. It is all crappy work and not a real database builder but its easy work as polypropolene carpets, little furniture to move so your hourly rate will be higher.
Mark