red,
I've worked for estate agents and letting agents for about 10 years and can tell you 2 things,
1, most letters go straight in the bin or are opened by the wrong person,
2, they won't be interested in the money as most costs are passed on to the client.
Believe me i know as i tried it myself.
You really need to go and speak to the manager in person.I tried this are many failed letters and after two weeks clocked up about 8 agencies and none of them remembered seeing my letter.It's really quite hard going in face to face but it is really the most effective.
also most of the agencies encouraged me to increase my prices so long as i did a good job and was reliable, one of the things the look for is being available at short notice, esp if they are closing a deal as time is money to them and that is what they will be interested in.
also be flexible, not many agents like working on a fixed price basis, but what you may lose on one you gain on another.
all in all you have to go and thrash out the needs of easch agent, as they are not all the same but they do appreciate the personal touch.
I've been working for the same few for last 10 years and it does provide some steady income, but do be prepared to get some rough jobs
regards
steve