I have a 4-unit property in Maine that I provide heat & hot water that are currently off of the oil fired boiler. 

The Solo 401k also offers a lot of benefits over any IRA when it comes to using the account such as the ability to borrow from the account, contribution limits about ten times higher, spousal participation, built-in Roth components, and additional tax benefits.

If you can't separate utilities, then the "main" original part of the house would be paying the smaller units utilities. 3) Fairly splitting the parking and yard space is another issue that comes to mind

The main requirement is that any property purchased in an opportunity zone must be purchased through an Opportunity zone fund.

These stuff often do not depend on the neighborhood Class, but the construction and materials used, and the already used life span of the systems/components itself. 

@Jared Smith I own 20 units and also mainly work with investors as an agent!

Cap rate and price-per-door are two of them.But your main concern is not finding deals in your local market, Denver. 

But FHA is the main law you need to worry about.

For those with previous commercial real estate experience, what main things should I be looking into or asking?

The main reason is the challenge you'll face when trying to resell it later.