Hi @Nilo Gabales Samson, welcome to the site!
To estimate the ARV (After Repair Value) of a property, you must find the most recently sold comparable homes near the location of the property you are interested in. You must compare the home you are interested in with these recently sold homes that have the same amount of bedrooms, bathrooms, square footage, lot size, etc. as your subject home. In my area, you can go to web sites such as realtor.com and zillow.com and search for "recently sold" homes, make the criteria (beds, baths, sq. footage, etc) the same as your subject home and narrow down your list of comparable homes pretty quickly. By doing this, you will know roughly what homes that are similar in size, build, and finish as your home are selling for. By the way, there is several pages dedicated to showing you how to estimate ARV in Brandon Turner's book, http://get.biggerpockets.com/nomoneydown/, I would suggest reading it.
When you've done that, the next big thing is knowing what repairs the home you are interested in is going to need, and how much they will cost. That is something that is different case by case, and if you are not very familiar or knowledgeable with construction/remodeling, you will need to have contractors come out and look at the homes with you and give you a cost estimate of the repairs needed. A very good, thorough book to read that will help you to understand construction repair costs is J. Scott's book http://get.biggerpockets.com/flippingbook/.
Hope this helps you!