How accurate are the "estimated monthly" on real estate sites?

[Damian Valdez]

Hey everyone, I just got done reading "How to invest in real estate." I like how it gave you a few things to just start practicing a few times a day. One of them is to get involved in these forums so this is my 1st post. Another thing to practice is calculations and this is what this post is about. I found a duplex that's 200k, on these sites is shows "monthly payment" that includes principal and interest, insurance, and property tax. 

How accurate are these numbers?