What’s your advice, lessons learned, experience in this space?

In these situations, when we pull a toilet, we shore up the floors install access panels, replace the usually either non-existent or non-working shut off valves and then install a high-efficiency toilet and make ceiling repairs.

Colorado Springs and Denver have seperate MLS access - so if you use one Realtor make sure they have access to REColorado (Denver) and PPMLS (CO Springs).

By comparison, your unit is larger and has a private yard space.

Working with a broker would allow you access to guidance and mentoring which sounds like something that would be of value to you right now.

The house doesn't have access to a street, it is in an alley.

For example, if the city has a multifamily measuring 3000 square feet of living space, will the total square footage of the three condominiums also equal 3000, or is a different means of measurement used. 

I'm looking for a 2 or 3 unit property (of which I would occupy 1 unit) with access to parking in a decent neighborhood within Hudson, Union, Passaic, Bergen, and/or Essex Counties. 

If you cannot get access to the property for an appraisal, you won't be able to get the underwriting completed.

They don't run gas lines in the winter and I don't think your tenants would want to use space heaters for 3-4 months.