Realize you are likely going to use CA Fair Plan (due to fire risk) and that is not cheap.  

What is a fair offer to make to that GC, and what kind of deal should I not accept?

We recently sold a rental in Columbia, SC and did fairly well.

For primary residences, taxes paid equal 4% of the fair market value of the home times the local millage rate plus any other local district taxes assessed, such as for fire or police, but with a school district tax credit.

The Fair Market Rent (FMR) on the HUDuser.org website is the Median Rent for the are based on actual rent surveys. 

Since you're in Florida and the laws are much more fair, I'd be willing to take a chance if his background/credit check came in clean. 

You can also look at creative financing/subto or owner finance as an option and finally there are DSCR options that will allow you to go up to 85% of purchase (but there is a fairly severe interest rate penalty), so I'd recommend staying in the 70-80% range.

if something is just sitting on the MLS looking too good to be true... then it's too good to be true.these properties are going to have higher costs overall, be in more challenging neighborhoods, have very gnarly deferred maintenance and capex, potentially have liens, be high turnover, and require expert, highly knowledgeable, localized support to be successful. see for example this thread.https://www.biggerpockets.com/forums/48/topics/1137397-balti...and even at those price points, i think cash flow is fairly low to non-existent if rehabbed to a high grade, especially with DSCR debt. 

Get the remodel done, pay people fairly, and get out of HM as quickly as possible. 

It’s priced what would seem like very fair relative to comps in that same neighborhood.