Estimating 4-plex value and deal analysis

[Joshua P.]

Newbie real estate investor in Las Vegas and first time posting. I am seeking out 4-plexes and found a property listed for $420K, monthly rent $3600. Net operating expenses about 12-14K. 3bd/1.5ba half a mile from an elementary/middle/high school so seems like it would attract long term family renters. 

I've run the numbers several different ways and it looks like it will cash flow $600+ a month even in worst case scenario. I'm considering putting in an offer but I don't see a lot of other 3bd 4-plexes in the area selling (mostly 2bd). What is the best way to estimate what an appraisal will come back at? And does this sound like a good deal? Posting a copy of my purchasing terms sheet for feedback: