Some options are paying in cash and pulling the cash out once the property can have an appraisal that will be marked "as is" (so no work needs to be done to the property to make it habitable). 

if an appraisal comes in low and it doesn't work out? 

I agree with Bruce.If they were up to code when installed they should be fine.That said I like to get my own inspection and appraisal prior to listing. 

-Contractors not performing, low appraisal, unforeseen renovations, finding a deal that works, offering the right price based on financing and timeline, materials selection, contractor management, contractor vetting and selection, contractors contractors contractors...This is not an easy game to buy and hold multiple units.

But Flood insurance is required as primary ($2000 / yr)By the time I fix and sell the home (8-12 months estimated) and incur additional costs + holding vacant, and selling expense (SQUATTER RISK, <100 miles to MEX border), and then go back and recapture depreciation + Capital Gains... my TAKE HOME will be far less than the appraised market value. ~50% haircut.So... since all goes to charity in 15 - 20 yrs anyway... why not donate now and play those cards?

After you have the lease signed, they will do an appraisal.

This would help you see its value for resale or appraisal for refinance and help determine the level of rehab needed. 

Redfin was showing a home sold for 280k but after seeing the appraisal it  actually sold for 250k.

How is the bank covering $490K what is the LTV and what did the appraisal come in at $490K or less?

Appraisal last January was 640,000.