Need to attract advertiser leads to advertise on phone app dealing with real estate repairs

I'm releasing an Android phone app that will calculate the repair cost of homes. I need contractors related to home repairs such as handyman, electrician, plumber, painters, roofers, flooring, ac tech, etc.. to market their company on the app. I would like to use social media attract contractors to give our app a try. We are offering a 2 month risk free trial period to contractors to try it. My goal is to have 100 contractors in 100 cities in the US. I will focus on one city at a time in the marketing. On your bid, let me know the amount of leads I can expect from this type of marketing. Let me know how can I measure your sucess. Amount of time it will take.