If there’s a cast iron or similar tub there already then I’ll tile it.

Cast iron and clay need inspections.    

I am exploring the passive invested rout or as they say in the pod cast the lazy investor.

Some things you can check:- are there any cast iron vent lines near your air intakes? 

As reference, current rents are at 47% of FMR (I know FMR is a guide and not cast in stone, but hey that's what I'm using it for, a guide)When underwriting and calculating the DSCR, Will lenders be using current, in place rents only?

Are you looking at properties near specific colleges or casting a wider net?

Cast iron drains can be scoped.

You generally need permits when you’re touching:Electrical - i.e New breaker box panelsPlumbing - i.e removing cast iron pipes and replacing with PVCHVACStructural elements (walls, beams, load‑bearing anything)Roof workAdding square footage - i.e addition to the home or conversionAnything that changes the home’s layout or safety profileThose items can impact insurance, inspections, and liability, so pulling permits protects you long‑term.Cosmetic work usually doesn’t require permits, like:PaintFlooringCabinetsFixturesTrimAppliances (unless rewiring or re‑plumbing is needed)Another thing to factor in is your exit strategy.

For a triplex where you're likely dealing with cast iron drains and potentially knob-and-tube wiring, budget anywhere from $30-60k for a full systems update if that hasn't been done already.That said, the flip side is that properties like this often have tremendous character that commands premium rents in walkable downtown areas.

If you look to replace cast iron as you anticipate it failing keep in mind no one can use the plumbing when you do that so figure on how to manage your tenants.