If you have never built anything significant in a seismic region you should stay away from imagining costs for 2-story additions in earthquake country.

And the structure/foundation will be inadequate by today's standards, but unless you're in an earthquake zone, that ain't a big deal either.....

No Cyclones in the South, earthquakes, tornadoes, floods a little and the weather is the same as Tampa with a lot more wind on the beach.

They do work hard for the money, but they know the tricks on how to do the job and not do it all.Great example, yesterday the appliances came in for a tri plex and I had to sign off and the installers hid the stove earthquake support underneath the  paperwork ( warranties).   

Even though a majority of the custom homes I did wanted tankless because they were cool and green....Most tanks last far longer than the expected 10 years and the new ones are very efficient.....Did a search ...https://www.consumerreports.or...Main takeaways are: 1) they are very close to the same cost to operate per year 2) the payback time on the tankless is about 25 years.....Plus tanked heaters are a good source of water storage in the event of an event like earthquake or such.....

I would look at an earthquake situation myself before I guessed a tenant did it.

The structurally bad part is that we have small, unnoticeable earthquakes all the time and the basements then didn't have rebar, adequate thickness, or good footers.

It's a common enough thing in most homes and while I've never been to Cali I imagine it's even more so common with all the earthquakes I hear about!

High interest rates of the early 80s and Savings and Loan crisis which spawned resolution trust .  2.  1989 regional to mainly CA  was earth quake and war    3. 1999 Dot com bubble which hit N.

Unless we have a earthquake large enough to dislodge the piers.