On the other hand, renters are paying the notes so who cares, and a 30 year note would mean lower montly payments, thus a higher monthly cash flow, more houses bought more quickly. 

From there, I read Dave Ramsey's Total Money Makeover, but I didn't care for this book as much.

Very few renters will care about it being finished or insulated, particularly in a warm climate like California.

@Cameron Belknap FHA loan rules in HUD 4000.1 mention not counting the basement as part of the Gross Living Area; however, part of the FHA requirements found in HUD 4000.1 includes a section on “converted spaces” which states:“The Appraiser must treat room additions and garage conversions as part of the GLA of the dwelling, provided that the addition or conversion space…is accessible from the interior of the main dwelling in a functional manner; has a permanent and sufficient heat source… and was built in keeping with the design, appeal, and quality of construction of the main dwelling.”Furthermore,“The Appraiser must analyze and report differences in functional utility when selecting comparable properties of similar total GLA that do not include converted living space.

Nobody cares about your property as much as you do.

You did not mention the age of the property  you are looking at and that could make a difference if anything might need special care today like asbestos, lead paint, and the major draining system. 

The IRS doesn't care if you have leverage or not when you take deductions (unless it's IRA money).

With self-directed IRA the sky is the limit.Of course you must be aware of the IRS prohibited transactions and be sure to stay away from those:https://www.irs.gov/retirement-plans/plan-particip...Selecting appropriate investment option depends on many different factors such as your age and investment horizon, your risk tolerance, investment experience, etc.

I have never made one and I don't care to make one.

Careful walling off "units" in a SFH in the City of College Park unless you're owner occupant and renting part of your house.