I'm a fan of quads because, typically, the cash flow is a bit higher. 

I'm currently exploring opportunities in both the Southern California and mid-east markets.Another consideration on my radar is the prospect of "Owner Occupying" my inaugural multifamily home in San Diego, with plans to expand my portfolio from there.I would greatly appreciate any advice or insights from those with experience in the field.

I would not pay above appraised value for an investment property unless I knew it had some competitive edge that would increase its value considerably (ie. it was a subdividable lot or allowed for other uses that enhanced value that were taken into consideration).

If you are investing for appreciation over a long period of time vs. cash flow now, and you are happy with your investment then all is good.

There’s no secret formula out there, you will find it near impossible to cash flow with these rates almost anywhere in the greater dmv, you can put more down, you can eat negative cash flow, you can invest in another market (I like the eastern shore, though even there you are probably breaking even at best) or you can put your money in a different asset class, the market decides your return’s for the most part, not you. 

@Christopher MooneyHere’s my take …Looking at the book in the NOI section:     Cash flow after taxes = Cash flow before taxes – Income TaxIf by “Net Income” you mean “Cash flow after taxes”, we can restate the formula as     Net Income = Cash flow before taxes – Income TaxThe formula applies at both the portfolio level and the individual property level.Since you have taxes of $3,000 at the portfolio level, and if you know the “Cash flow before taxes” at the portfolio level, you can determine the portfolio “Net Income”.If you knew the “Income taxes” and “Cash flow before taxes” for each individual property, you could calculate “Net Income” for each."

Are most lenders looking at my W-2 history and DTI to determine whether I qualify for the refinance or is it more based on the asset and/or its cash flow?

Timothy - Here's one approach for your consideration - a lot of good advice on this thread. 

Your financing method is important, as interest rates will significantly impact your cash flow. 

Cash flow is possible in most areas, plus appreciation potential where you go.