I used to look at Cash-on-Cash, but it's guesswork...returns on paper and actual property operations are vastly different...it's generally impossible to get accurate with CoC unless you are buying with cash...even then, it's not a good indicator of value...my personal first level filter is the relationship to purchase price and rents...I see too many investors analyze themselves out of the market because they cannot get their number to work...

For an array of reasons. 

The vast majority of them are likely honest, high integrity characters with great advice and a story and information worth learning from. 

The vast majority will not try or there will be no money to recover and landlords will have to eat the loss.   

I’ve flipped in the dc area for years, right now there is just money & in the vast majority of cases there is high likelihood of losing money, right now the best investments in the area imo are buy & hold, I’ve even gone full circle and while I really liked value add for most of the last decade I think in a lot of ways new construction especially in more affordable markets (I’m personally a big fan of the eastern shore market) is a much better way to make money long term than flipping and brrring while I know they are sexy & certainly you getting a huge paycheck is great, there just isn’t any money in it right now, especially in nova.  

This appraiser was from Ohio, which has a vastly different rental market than here.

I've looked at similar properties that are for sale or already have been sold but the numbers are so vastly different I'm not sure how to determine how much I could sell for. 

You wont knock it out of the park, but a solid earnings stream might be had.The other side of the coin is a poor TK provider might sell you a property that has hidden issues and a poor tenant in a sub optimal neighborhood.I don't think its one or the other, I think the vast majority comes down to  the integrity and market conditions at the time you buy.

When you say California, you're talking about a very large area of land with cities that have vastly different characteristics.

It is nearly useless if applied to vastly different RE.