So appreciation (if applicable) may be another component to consider in the equation.

Off late I have been looking to expand in FL Hillsborough county/Westchase (Tampa area) seems to fit the profile of neighborhoods that align my strategy.

Contributions limits are roughly 10x higher, there is no custodial requirement for the 401k, you can take participant loans, you don't need the additional expense and administration of an LLC to have checkbook control, there is a built in-Roth component, a spouse can participate, there are additional tax benefits, there is generally greater privacy, and the plans are often quicker to setup and cost less money over time compared to most IRA LLCs.

So you have to align you expectations a little more tightly to what you are targeting.

If you contract with a bonafide contractor they should supply you with a "line item estimate" explaining the labor and material costs of the components they are installing in your project.

Maybe there's some way I can help, or maybe just see if/how our business goals might align. 

what are all the major components worth putting into the equation to figure out whether a multi-family investment property will be profitable?

They should align to your values as a person and a business.If you are uncomfortable to go alone on a first deal then I would suggest finding someone who has an active deal flow in your area of interest and maybe working for free (experience).

Giving my clients solid recommendations is a key component to helping my clients.

That said, I'm focused on cash-flow so aligning goals with geography helps.