So what number have you come up with for Capex based on that data? 

I'm wondering how this all went down without something unethical taking place...For your reference and anyone else's here, NAR Code of Ethics states:When an opinion of value is formed for a member of the public the opinion shall include the following:-identification of the subject property-date prepared-defined value or price-limiting conditions, including statements of purpose(s) and intended user(s)-any present or contemplated interest, including the possibility of representing the seller/landlord or buyers/tenants-basis for the opinion, including applicable market data-if the opinion is not an appraisal, a statement to that effect-disclosure of whether and when a physical inspection of the property's exterior was conducted-disclosure of whether and when a physical inspection of the property's interior was conducted-disclosure of whether the REALTOR® has any conflicts of interest (Amended 1/14)Also "REALTORS® shall be honest and truthful in their real estate communications and shall present a true picture in their advertising, marketing, and other representations."

What is the best method for an early stage real estate tech startup to get real estate listing data (in the U.S.) in order to to apply it to software and make it public through a web marketplace where users can connect with the listings original listing agent?

Once they pay, the accounting for the whole process is automatically entered into all of the accounting data software sections. 

The further I dug into the data and understood the property and market the more I realized it was actually a value-play deal!

My focus is on 3 bed 2 bath SFRs under $150k for buy&hold and cash flow investing.There is so much data online, that it's sometimes overwhelming to comprehend and correlate with what you are trying to achieve as an REI. 

What methods do you use to get data on livability for a property (schools, crime, employment, ...) in a relatively fast manner?

I think i did everything wrong on this first contact with the seller, i got nervous i didn't have my script ready.. but i am calling tomorrow again with data, hard numbers, an offer, setting an appointment to evaluate my offer and counter, and get that deal!! 

Then I did some web scrapping to pull the valuable data and stick them in a spreadsheet. 

You have the same baseline costs to keep the sfr functioning as a $9-1100/mo house, or even a $2200/mo house.Not really enough data provided..