I just had tenants move out of my investment property (duplex) without paying for the last month's rent, and the damage they inflicted onto the property exceeds their security deposit amount.

No free weeks, no reduced deposit, etc.

deposited in a demand deposit account?  

Beyond immediate safety concerns, the long-term financial implications, including taxes, are a pressing issue for those impacted by the disaster.

If you really want to get rid of them, sweeten the pot by offering to return their deposit after you verify the unit is empty with no damages. 

Lenders will want to see those funds deposited in a bank or other lending institution on one or two monthly statements.

And not being able to issue the deposit refund via Avail was the final straw for me.

Nothing you mention is "ordinary" and you should charge for all of it. dodged a bullet there thats a very good price take it from the security deposit and call yourself lucky. 

Now, I'm imaging a scenario when every one of these tenants move out that I'll be paying their entire security deposit + interest even if there are damages beyond normal wear and tear. 

TDAs offer peace of mind and a safety net, while real estate provides growth potential, tax advantages, and wealth-building opportunities.