How many letters is a big enough sample size to see what works?

[Anthoy James]

So I've started sending letters to nod's. This is my first week starting, I've sent about 50 letters since Monday (no calls yet, but I am tracking everything, hope to be getting more on the list soon). I'm going to send a follow up letter a month after I send the original, as well as a postcard after that.

In the meantime, I would like to start to market to a new group as well to test out different prospects and see which ones I'm getting the best responses to. I'm leaning towards either trying to get probate leads from the courthouse, or purchasing an inheritance list off USleadlist. What do you guys think of this strategy? For those of you who deal with inheritance leads, how many do you typically send?

Also, how many letters is usually a good indicator of how well a marketing campaign is going? I was thinking of sending 500-100 of each prospect group and going from there. Too many or not enough? Thanks in advance for the replies!