Especially during the winter, the hot humid air from the bath is going into the attic hitting the cold underside of the roof and condensing.

Thinking about replacing condenser only but honestly don't know the affected part.

Once the temps drop low enough and condensation begins, then you have water, not really humiditySure, basements are a culprit for mold (especially actually during winter time) because they tend to be damp.

Is the condenser covered by anything?

I agree central a/c is the way to go.But you will need the a/c condenser, a pad (or suspend it on brackets), evap coil, line set, electrical circuit & disconnect so you're probably looking at closer to $2500-$3000  using compatible Goodman parts & depending on what they charge to install it, (usually around $800-$1000).

If you allow pets, ensure your outside air conditioner condenser(s) are fenced to keep from the pets peeing onto them.

I would wait until the next rental group to be in before making larger changes like that unless it's just added a condenser to put in Central Air bc Central Heat is already in place and you need the tax deductions.

I think we only just replaced the washing machine & just replaced the original 25yr old a/c condenser.

There's no water dripping from above so I believe all of it is inside the chimney and there's condensation on the outside of the chimney now up to about 2 ft up.

My point is, and I hope this would never happen, but I don't want to have to pay a $75 service fee every time something starts going wrong not due to damage (e.g. leaky pipe/faucet, leaking water line behind fridge, leak from washing machine, clogged dryer vent, leaking water heater, A/C condenser fan gave out, furnace stopped working because the control board went out, etc etc etc).