Also, here in Idaho, they just created a new "First Time Home Buyer Savings Account" that allows you to deposit up to $15,000 per year (single) or $30,000 per year (married) up to $100,000 total — all of which may be deductible from your Idaho income taxes! 

Depending on the cost of the fix, I’ve often just paid for it and then deducted the cost from next month’s rent.

I don't want a 5 figure fee that cannot be depreciated or deducted as a cost of business.

You still are able to take all the same deductions.

That way you can keep accounting tidy and you'll know the true income/expenses of the property for property deductions for your CPA. 

There is a new 20% pass through deduction you may qualify for that could help you, but not everyone qualifies.

The things I would plan for are 1) ensure you have some type of flood and/or water backup insurance on the property and 2) plan that at some point it will fail and set aside reserves for the deductible and 3) plan for future replacement of the pump and generator.

If yes, maybe the property is a candidate for a cost segregation analysis - This doesn't increase your deductions, it just allows you to bring forward the depreciation to the earlier years.

Just because you put it in service later doesn’t mean you can not deduct your expenses.

If they have made any damage to the house/property based on the install/later uninstall you can deduct it from their security deposit when they move out.