He’d pay $50 - $100 for these, and wait thru the redemption period and then file for title.

I dont know the answer here, it is above my pay grade but if I were you this is where I would start.Talk to a lawyer.

Insurance would cover it, I would pay the deductible, and no assets would be lost.If you are in an area like San Diego where people are more likely to sue, a judge is more likely to find you guilty, and the payout is expected to be higher, you may consider an umbrella insurance policy.

I rented both, furnished them, and listed them on mid-term rental sites like Furnished Finder.

Willing to extend benefit of the doubt to someone packing up shakers (not paying attention), and yes, all this is small beans and easily replaced.

Are there calculators on this site that can calculate Net Present Value?

If I flip a house and make a profit after 6 months, then buy a new property 3 months later, what taxes will I be obligated to pay?

I would recommend BackFlip, but you do pay a little more on fees. 

I even heard of a landlord being sued and losing and having to back pay all the rent payments. 

Revisiting the subject of financing for vacation home/vacation rentals/STR's.  10% down is still an option without having to pay points.