In all cases I will show the benefit of time on local RE investments (even those purchased at full retail).  

Call your friendly local appraiser.

There is a clear, easy to read book, probably available at your local library or bookstore, by that name, and a website and an active forum, (of the same name) to ask questions and get responses.

Hi Flavia, Research the local market trends, economic indicators, job growth, and development plans in the area to gauge its long-term potential.

This means not only mapping the location of your existing utilities, but engaging with an experienced provider who knows how to work with your local utilities.

If you decide to further pursue this one you need a local structural engineer who can assess the already completed fix.

Hi  Nyron,I am local to the area and have a lot of connections.

Declining local economies invariably hurt home values.

Utilities, taxes (property, local vacation, & income), landscaping, furnishing / decorations / amenities, pest control, & supplies (soap, TP, etc) are the big ones on my STR calculator that you didn't mention.I'd also recommend using the enemy method to determine expected income.

Ask local property management companies what they are seeing for utilities for similar fourplexes.I don't know the age of this building but mine are 80s built.