All three units have a single small full bathroom with no windows.

Love the Sept-Oct window you mentioned and I believe you are correct.

We had a bump on the road as we took out permits to close out the garage and added 6 new impact windows, which all in all took about a 1 year and a half and costs more than we initially thought.

They quit using lead paint so long ago that there are probably many, many layers of paint over anything that might be lead.you can use a quality oil based primer/sealer on all the walls and any painted floors and then paint over that.Lead being in the paint itself, under many other layers of paint isn't going to hurt anybody unless they start chewing on your walls, and if they're chewing on your walls you got more problems than just old paint.Other places of concern would be window frames.

It was an open vaulted ceiling with floor to ceiling windows on a slab.Normally this wouldn't have been a problem, except in this house the owner had some electrical issues and decided to take the cheap way out to repair it by running all the wiring outside the walls in channels like you would find in an industrial application.

Window units might work if security is not a concern.

Second realtor was more investor-centric - giving feedback on what new windows would cost, and an average of what reno costs would be overall with contractors and whether his team could do the work. 

The windows have wooden frames.  

Move the stove to where the window is and move window higher (expensive as well)3.

People within that 2 or 3 month window, it's more like 70%, if I start deleting that more recent data, then I screwed up b/c there's about a 70% chance I would otherwise have actually used that information to help someone buy a home.