It took me about a week to get my license, start to finish- education, testing, forms, etc.

If OP elects de minimis safe harbor ("DMSH"), he's going to have to capitalize as the expenditure is going to be more than $2,500.If OP forgoes the DMSH and instead applies the Betterment, Adaptation, and Restoration tests ("BAR tests") under the tangible property regs, we'd almost certainly have a betterment and/or restoration of the HVAC subsystem on our hands, so we'd also capitalize under this option.OP may be able to use the safe harbor for small taxpayers ("SHST") to expense the costs, however not enough information was given by OP.If SHST is off the table due to limitation, then must capitalize. 

Inspection report tests prove it is in fact black mold but bc its in the corner and the connecting wall is finished we cant see if its spread. 2.

how to test this idea? 

Depending on what county you are in my answer can change but with the sympathetic press tenants are getting these days and the bad press landlords are getting I would not test my luck in legal cases right now. 

Those are subject to the FHA Self Sufficientcy test which virtually none will meet.

However now, all tenants are required to apply for assistance, or the landlord can do it for them, but if they don't get it in 14 days, you can evict them (we have not tested that last part).

Not as strong as an offer with no contingencies but I haven't had too many sellers (even bank owned / foreclosures) turn that down as it's a reasonable request.I bought a banked owned HUD property some years back, even with no water or electric turned on, the plumber can do an air pressure test to give a feeling of what needs to be done, and hire an electrician as well for a rough estimate.Although riskier, we wound up doing extremely well on that property.Good luck!

My grandfather never had a driver license he was from Europe, he seen his son (my dad) drive and grand children drive but he couldn’t it did not mean he didn’t know how he just did not know how to read and take the test.

FHA also has a self sufficiency test on 3&4 unit properties which less than 5% of properties actually pass it.