Ideas:- Request itemized invoices that outline the supplies, subcontractors, workers on the project, and materials purchased?

One item in a capex budget is floors.

The other item is that inflation and currency risk is a big problem in the Caribbean Islands and given that materials are imported the cost swing a lot.

Besides all of the items already mentioned about why its a bad idea, another is that at this point, it is likely that the contractor that I assume you are using on flips doesn't know the income earned on each project (they only know what their fee is).

It may be hard because the size of the rehab but get an GC to give you an itemized list of repair cost for your rehab and sub out the items you feel can be done cheaper.4.)

He has asked for fair market values for items that will be included in the study (ex: roof, water heaters, HVAC, cabinets, appliances).

In 2023 it will drop to 80% which means that in a cost segregation study, 80% of all items that qualify for depreciation in 5, 7 and 15 years can be depreciated in the first year (just like the 100% Bonus did) and the next 20% can be accelerated to the appropriate category: 5, 7 or 15 years.

See if they can give you an itemized scope of work.

Go over the bid line by line and decide what repairs you need to move forward with and what you don't need and remove the unwanted items from the bid. 

The true value of RE is in what those two items represent in the form of future cash flow and property value.