By the numbers, the cashflow may look better, but the turnover tends to be higher and you have a whole new set of CapEx expenses that have to be supported entirely by that one likely lower-rent unit (it needs its own water heater, HVAC, roof, etc.)If the property isn't a great deal without the garage unit, it won't be a great deal with the garage unit.

Very old and tiny 2/1, but no major upkeep needed in short term as roof, water heater and furnace are all newish.  

.- Water and sewer capacity fees (locally ~$10k just for approval per new dwelling unit).- Sewer sizing.

That water heater is costing you $100  year. but you don't see that cost for years down the road. 

I really appreciate the help as we begin to navigate these waters!

I drink a gallon of spring water daily. 

Ask me how I know this....2) the hardware at ikea for cabinets (drawer pulls, etc) is not the best, and needs some patience and tweaking, but can give you a really, really cool look for a lot less than custom.  3) if and when someone tears through the outer laminate (plastic) layer on them, water will destroy them in no time (think under-sink leak)

I just bought my first investment property and now my mouth is watering for more.

Also find out if this is on city water and sewer system. 

And no it is not just pure speculation to invest in CA real estate ... there is a science to it and done properly it is highly repeatable.