During the beginning of the stabilization, we had a HUGE FIRE roughly $400k in damage...well after the fire our property manager did not properly secure the building and then the locals came in and stole all of the radiators, which caused leaking through the entire tier. 

I would focus on getting that househack first.You can take advantage of a lower downpayment, get a roof over your head, and an investment property all in one.

After a thorough review of systems, we had plumbers troubleshoot and repair/replace a couple of small chronic bathroom leak issues, and electricians installed a number of end-runs back to the panels so that rooms could each have window A/Cs running without tripping circuits and other such issue.

I sold a beachfront home last year that was ICF constructed in 2000 with a metal roof on concrete pilings and the insurance went up triple what my larger 2019 stick built with shingle roof 6 lots down is. 

If you are buying a house of any kind with mechanicals and roofs, you need reserves.

With your estimate, you might earn $800/month for 2 years and then incur a vacancy at the same time as you need a roof replacement and for that tax year your cash-flow might be -$1,200/month.

There's no roof or sewer for you to manage.

Is this a decision about one or the other - either write off the old roof OR depreciate the new roof? 

Last year on one cabin I had to replace the roof, hvac, & tile shower which came out to $22k.  

Has a unique garage that is open air, but  roofed and on the same slab as the  rest of the house.