On most properties I evaluate here are the key factors I use in determining value:

1) three same-like properties. comparing single family houses to single family houses and not duplexes for example
2) same approximate square footage
3) comparable properties within 1-mile of subject property.

Of course my methodology is more detailed than that with the forms I teach in my course, but basically you are looking to get an average "retail" value per square foot. From there, you should mutliply that average retail value per square foot by the number of square feet your subject property has. That should give you a rough estimate of the ARV (after-repaired-value) of the property. Of course back out from the retail amount any repairs needed, holding costs, and lastly YOUR PROFIT to find out if there's any equity/profit in the deal.

Thanks,
Scott