In the end it will all come down to the pro forma analysis and the accuracy of your ability to correctly gauge the correct rental rate.  

Zillow isn't known for its accuracy.

Thanks for the info George, but my question is, how would I be able to know the accuracy of the "gross sales" since a lot of times I've found it to be inaccurate?

Your degree of accuracy has to be a lot higher for value and type of land you're buying, so environment as well as location plays a huge factor.

Also really investigating the properties by parcel number and legal description, seeing as the county will not guarantee accuracy of information provided.

Although I'm a marketing guy, I'm not currently mailing anyone else's list(s) right now however I've been mailing since 1978 so I guess that makes me qualified to comment.The big challenge with compiled lists, beyond accuracy, is that they are static lists.

I also know that on my next deal when I start crossing all the I's and dotting all the T's that I make sure that my team can do their part with accuracy.

Okay, I cannot vouch for the accuracy or how easy the interface may be but have you checked out Houseflippingspreadsheet.com?

The most decisive factors are the accuracy of your rehab estimate and ARV.  

@Bob Bowling   I still use a stick for accuracy.. just have to make sure you use Jet A when needed or 100LL when appropriate wrong juice can ruin your day