It's not a big deal to clean the drains and coils, you just need to make sure it gets done.

I also get my units serviced once a year or so and they clean the coils.

I prefer to replace from the outside where you have room for some errors so you can cover with trim coil if it happens.

We'll get the doors and windows on before we bring any finishing materials on-site, we'll hold off installing the compressor and coil until we're ready to list, and I imagine we'll use our Lasershield portable alarm at some point until we get a real alarm system in there.

FWIW I've seen inspectors miss alot too, cracked heat exchanger & plugged fan coils in HVAC FAU.

The heat coils can address this.

New Lineset will be ran through attic and new coil will sit on existing furnace.

There were never any complaints about mold and they also forgot that they are responsible for changing AC filters every month, cleaning the AC closet door and also when the AC was repaired, it was also professionally serviced, coils and condenser fins cleaned. 

For the outdoor unit, 6 indoor air handlers and other supplies (cable, copper,etc), it was over $7500 in supplies alone.I installed a regular heat pump instead with a 20KW electric coil for emergency heat.

I also agree with making sure the coils are clean.