This formula is meant to help assess the deal before a purchase.This formula is for purchasing purposes.

In 2008 the IRS set forth a safe harbor rule under which it said it would not challenge whether a replacement dwelling qualified as investment property for purposes of a 1031.

Your risk for being checked is higher on multi-units as normal people dont do this and only want them for investment purposes. 

However, you need to establish relationships first, there is no magic list.What is your purpose for finding IRA investors? 

For vacation purposes, I'd stick to the beach towns in SoCal you mentioned or the cities already recommended by others above in NorCal.I love California.

I invest at least 10% of my investment portfolio in metals for hedging purposes not income. 

There are many who get bogged down in trivia and lose track of the purpose.

For a city in my area:In every dwelling unit and in every rooming unit, every room occupied for sleeping purposes by one occupant shall contain at least 70 square feet of floor area; and every room occupied for sleeping purposes by more than one occupant shall contain at least 50 square feet of floor area for each occupant 12 years of age and over and at least 35 square feet of floor area for each occupant under 12 years of age.

For tax purposes, the real estate professional designation is something that is very helpful if you are an investor.  

Are you referencing the property assessment with the city or county for tax purposes?