Besides the deep pockets, Big Data with Artificial Intelligence gives them Data. 

https://www.redfin.com/blog/data-center/

I usually use trend graphix but they only go back 15 years and I'd like to go back 30 years so I was looking at the case-shiller home price index and after trying to find the answer on my own, I cannot figure out how to convert this data into percentages. 

It's not perfectly accurate- sometimes the data's a little outdated, but sometimes it's spot on. 

These data points are key in maintaining realistic and understandable valuation for the real estate market.

CurrentlyI've spent time writing my mission statement, setting my goals, planning my long-term goal, and running data (thank you, BiggerPockets Pro Calculators!)

:I have run many different scenarios via excel and ultimately if we are talking buy and hold, your properties in California will make you very wealthy and to even come close to what the complete roi would be, you’d have to buy hundreds of out of state properties...What data are your scenarios based on? 

(remember, rockstars know other rockstars) Ask some questions about the job growth and local data you have read about to confirm it's all legit.

Just found a client from my data base yesterday, so he’s very excited about it.

Would want as much exact data plugged in as possible.