The numbers you list are somewhat helpful in finding a neighborhood (and the short answer I'd give is zillow.com for some neighborhood comparisons), but I wouldn't rely on them for finding a specific deal. For each deal you need to know several numbers in particular to determine the maximum amount you can offer for a house:
ARV (after repair value) which is basically what you're going to sell it for. For that you need comparable houses, and zillow.com works okay for this as long as you're only having a look at what was recently sold. Make sure you use the filter on the side to narrow it down to recently sold houses with the same number of bedrooms and bathrooms as what you're looking at and you can get some idea of what things have been going for. A realtor can provide a better list in my experience, though.
Profit: Simply put, how much you want to make on a house. This number is subjective of course.
Rehab cost: You'll need to be able to estimate the cost to bring a house into move-in condition. Some of this is intuitive, some is learned. Most people could guess that an average water heater will ballpark something like $500, and there are some formulas for determining other items (for flooring we budget $2 x square footage of house). Sometimes a local REIA can be very helpful in this, as commercial members looking for business may be able to give you some guidance in regards to costs.
Holding costs: How much it costs to keep a house while you're working on it and before it sells. The mortgage has to be paid along with taxes and insurance until you sell it. This is dependent on how much you paid and how long houses sit on the market in your area. The first you can figure out easily with an amortization calculator. The second is information a realtor would have easy access to. You can also do some driving/walking through your neighborhood and the sheets offered in the information packets for houses have quite often had the CMOD (current days on market) number on the sheet as well as the date the report was run. From that you can just work out yourself when the house was listed. For my area, just using a much simpler formula like 1% of ARV per month is pretty close for mental calculations.
Hard money costs: Will you be getting money from a hard money lender? They're more expensive than a conventional loan but if you need money fast for an investment property they can be useful. They often charge a few points along with a higher interest rate so that causes you to come up with a different number for your holding costs.
Realtor costs: Will you sell your house by owner or use a realtor? Assume 6% of the ARV will go towards that.
So from all these numbers you can work backwards from the ARV to the maximum purchase price.
Maximum offer = ARV - profit - selling costs - holding costs - rehab costs
As you can see this formula has nothing to do with the asking price of the house in question. In my limited experience, it's just not possible to determine if a place is a deal or not by looking at the asking price and location, plus you don't know what they may or may not take. But once you can more or less figure it out in your own mind as you're touring a house, you can make an offer on every house you walk into and know that you're working a reasonable profit into any place that you potentially purchase.
