Reliable Comps and Estimates

[Augustin Tommy Jr.]

Hey, I've been doing tons of research over the past few weeks and would really like to get started in Real Estate Investing with my entry point being wholesaling, however, I wanted to know where is the best place for me to be able to get comps for a property. The reason I ask is not only for my sake, but for the sakes of potential buyers out there that may not be highly experienced. I don't want to end up unknowingly screw somebody over due to simple mistakes. 

I know Zillow and Trulia are big no nos, and have heard that getting CMAs? from a realtor is the best way to go, however I'm unsure about any possible associated costs with that. Any help or further clarity would be greatly appreciated!