Hey everyone,
To get to the point: I have an old house in PA, and groundwater is continually intruding/pooling in my in-slab/sub-slab HVAC air intake vents (floor returns). Yes, this is a thing, as the house is from ...

If the shower walls are already showing moisture intrusion and mold behind the tile, you’re not dealing with a cosmetic issue anymore.

The key is stopping water intrusion and having a contractor who guarantees their work.Taking the extra time now prevents headaches later and helps ensure the shower lasts for years.

Lenders won’t ignore structural or water intrusion issues — they’ll want to know exactly how and when these will be corrected.Also, not being able to see the upstairs unit is a concern.

The foundation inspector stated that the foundation “appears sound.”After closing, a neighbor informed me of troubling details: The previous tenant had water intrusion issues near the windows during rain.

Leaks, water intrusion, dampness, or mold indicators.c.

I've read that adding a layer of drywall helps more, but it's a more intrusive process.- Be clear/upfront about it in the listing description and the photos. 

Potential issues like basement water intrusion. 

“Do not let wet clothing or towels sit for long periods — they can cause black stains on walls or ceilings.”Have tenants sign a Mold Addendum acknowledging that they understand their role in preventing moisture issues and will notify management promptly if they see any black stains or experience leaks.Landlord ResponsibilitiesAddress leaks, water intrusion, or condensation issues immediately — prevention is key.Hire licensed contractors for roof, HVAC, or plumbing repairs.Keep documentation and photos of all tenant complaints and maintenance actions.Maintain proper ventilation and dehumidifiers in basements or areas prone to moisture.If mold is confirmed, notify tenants in writing about the remediation process and timeline.Tenant ResponsibilitiesReport leaks or water damage as soon as possible.Use ventilation fans during and after showers or cooking.Maintain reasonable cleanliness and avoid over-humidifying the space.Follow the instructions in the Mold Addendum and cooperate with access for repairs.Final NoteMold prevention is a shared responsibility between the landlord and tenant.

@Miguel GonzalezEvidence of foundation issues or water intrusion would be a concern.