How many leads for first direct mail campaign?

[Andrew Herrig]

I am about to start my first direct mail marketing campaign and was wondering how many leads I should start with to have a pretty good chance of closing at least one deal.?

I am planning to get an absentee owner list for 2 or 3 zip codes in my area (Dallas), with >50% equity via Listsource, and start a 6 month campaign, mailing once per month, alternating yellow letter and postcard. I am estimating it will cost ~$4 per lead over those 6 months if I do the work myself. Does that sound reasonable?