#1 Mashvisor.

#2 Allpropertymanagement.com.

#3 Homeaway.com and Airbnb.com.

#4 BiggerPockets.com.

#5 flipthiswholesaler.com.

#6 Trulia, Zillow, and Loopnet.com.

#7 Redfin.com.

#8 ZipRealty.com.