You have to go a little farther down Glenway towards rapid run before price hill gets nicer. 

The windows are old, as is the house and it is typical for them to be drafty, they will more then likely not be off the shelf windows however Menards lets you custom order JenWeld windows any size you need down to 1/8" increments with really no extra charge in case you decide to swap them out.

I started to take actions on the following steps and making incremental progress. 

Quote from @Brandon Yamada: I never recommend incremental rent increases.

Generally, any property that is 5 or more units is considered commercial, but you may also see incremental tax increases on 3-4 units depending on your insurance coverage.

My home's value in Mira Mesa is rapidly approaching the highest it has ever been.Swanny

First off you have to generate excess cash flow in a rapidly appreciating market.

I am focusing in the Grand Rapids area specifically. 

The population has been declining rapidly for some time (there are now twice as many Puerto Ricans living on the mainland US than there are on the island).

Rapidly scaling up your investment portfolio requires robust management systems and capital investment.If you are working full time, I would recommend you hire a property manager to manage your duplex.