Fist of all I will check if there are any leakages from your negligence of maintenance.

There have been minor leakage issues in the past and some minor weather damage issues as well that I can probably leverage off of to bolster the case for expense characterization. 

Closing is set for this Tuesday but there's some evidence water leakage in the garage where the furnace metres the ceiling.

I'm a tenant whose apartment (HUD subsidized) unit has seen leakage of water (probably due to leaky pipe) on the floor from the wall in the living room due to rain.

Piping / leakages / etc. 4.

The mold she was talking about was a roof leakage 3 years ago, which we hired a company to fix it. 

A good seal will prevent water leakage. 

A normal vacancy clause excludes theft, vandalism, water damage, attempted theft, sprinkler leakage, and glass breakage if the building has been vacant for over 60 days. 

There were several issues noted as relates to the roof including staining in the ceiling of one of the closets and moisture noted in the attic....That to me suggests current and past leakage...something that was never disclosed.

If you are not prepared to bring the unit up to a quality standard now, assume the tub surround issue is a likely indicator of leakage issues and possibly wood destroying insects as well, so start saving now for a big expense, and evaluate the overall plumbing and electrical systems (including replacing old outlets, switches, fixtures, and correcting any improper "handyman" work performed over the last 20 years by the prior cheapskate landlord) to plan for costly updates there.