MLS vs Zillow & KPIs

[AJ Sherman]

I'm learning away with all the great forum posts. 2 newbie questions:

1) I was listening to one of the podcasts and it was stated that apps like Zillow, etc. are not good for analyzing numbers and deals. The only way to go was direct access to MLS. Dont Zillow and others apps use MLS data? Why would their data be bad comparatively?

2) I'm about to dive into learning the numbers. I'm going to check out the Intoduction To Realestate Analysis and Frank G's What every Realestate investor needs to know about cash flow...and 36 other key financial measures. Any other recommendations?

Thanks.