Many people automatically think electric resistance baseboards (or electrical coils in a central air-handler), but your ancillary heat could be easily fuelled with natural gas, propane, oil or another fuel.Presuming your use of "furnace" means a forced air furnace and not a boiler and hydronic heat, you have the option of adding a heat pump with an exchanger insert in the plenum of your existing ductwork.  

How does everyone handle rent increases with new home purchase, with existing tenants?

Your results/experiences will be based entirely on the handlers in the local welfare office.

You will be competing with Realtors, but that's an easy objection handler! 

I will probably hire out for that work as I have minimal exp with siding and none with stucco but can learn.The AC handler was replaced last year and the condensing unit motor as well.

The two other methods I am aware of are installing a motorized main damper to direct flow to the area calling for it and hydronic boilers driving several remote air handlers.

Just curious if there might be some objection handlers I should put in my back pocket for the future.

A new air handler isn't much more than that.

Rental handle Property handleReal Estate handleWe will handle your....Get a handle on....

The contractor I used on my last project wanted $11,000 to install a new 3 ton heat pump (brand new system, new compressor, air handler, run duct, etc) in this house.