With the situation you're going through, your first thought was likely "I'll raise the rents to cover this." 

If their policy ever lapses or is canceled, they are automatically enrolled in my master policy and covered. 

I think #2 covers 90% of the work, BUT there are people whose debts are out of line with their income.

That covered pretty much everything! 

The projected rental income wouldn't cover the mortgage and HOA at this time.

The main factor is will rents cover the debt liability and can you sustain 3-4 months of no income to cover the debt? 

In the case where those assets did not cover the costs for the line, would that lender also have a clawback clause that allows them to claw at other assets?

Each lot is assessed with the taxes to cover such cost and they are paid monthly for the first 15 (give or take) years as part of your mortgage payment.

You will need to cover perc tests if needed for each lot and then hire a surveyor to draft the ANR plan for submission to the town, just treat wetlands as sacred Indian burial ground - stay away from them and your costs will be very low.  

STR management is 20-25% (I would recommend self managing or getting a VA), since income is higher you could probably get away with 5% for maintenance / cap ex but remember you need to cover utilities and cleaning for these units which drives up costs.