I myself, like many others, started with a purchase of a condo, then to a single family, then to a 2-4 unit, now to commercial multi-family with 5+ units.Figure out your goals and why you want to invest and work backwards on how you can achieve those goals.

@Josh EngelhartIs that the same if it goes above 5 units and is considered commercial?

Bedrooms require access to natural light and natural ventilation.

The more successful San Diego OOS RE investors that I am aware of are mostly into commercial multi family (5+ units).  

Just remember that you need access to capital to keep doing deals so if you are limited on funds and tie it up in a rental property that makes you an extra few grand a year you may be limiting yourself to doing other projects.

This becomes several times more valuable when you get into commercial as those deals become much more complex.

My background into RE started when I began working as a commercial credit underwriter for a bank.

I do commercial but for residential what I saw on the last down cycle was this.Those landlords that had the most expensive rentals felt the pain first.

My wife and I both worked for nearly a decade for a commercial property company focused on leasing and sales in the retail sector so personal real estate investing was always a path we knew we would pursue having seen first hand the wealth real estate can generate. 

Otherwise, some book recommendations (these include mostly books on business/lifestyle or buy/hold investing):- "E-Myth Revisited" by Michael Gerber- "Rich Dad, Poor Dad" by Robert Kiyosaki and Sharon Lechter (this provides a more foundational perspective on money)- "Cashflow Quadrant" by Robert Kiyosaki (further builds on the "Rich Dad, Poor Dad" foundation)- "Set for Life" by Scott Trench- "Long-Distance Real Estate Investing" by David Greene- "The Book on Managing Rental Properties' by Brandon Turner and Heather Turner- "The Miracle Morning" by Hal Elrod-"HOLD" by Gary Keller (geared toward SFR)-"The ABCs of Real Estate Investing" by Ken McElroy (geared toward commercial investing)"Multi-Family Millions" by David Lyndahl (This is on my list of "To-Reads".