I think new builds don't really work from an ROI standpoint, but if you can find properties that have easy ADU conversions then the value might be there.I'm in MA and we just made ADUs legal by right, so I'm looking into the best ways to add value using them.

This reduces your housing payment and helps you build equity. 

I'm just beginning but am considering a bigger commitment in the next five years or so by accessing some or even all retirement funds to buy a building (I'm sure people have thoughts on whether or not that is a good idea!).

Depreciate 75% of the building value (excluding land) over 27.5 years for significant tax savings.

If the property has solid appreciation potential or you're building equity while learning the ropes, it could still be a good deal.

I’ve done a couple of fix and flips but I’m looking to build a rental portfolio.

A lot of people who househack do so as a basis for a strong financial future and to build generational wealth and financial freedom. 

You'll find the most success in a place you are familiar with and where you can build a solid team.

I live in Lebanon, IL and this property is also in Saint Clair County in Belleville.I plan on managing this at first, but want to build a proper amount into my budget.What would you recommend for budgeting for in terms of good property management in this area?

Your best route might be to buy a 2 to 4 unit property that you can live in and rent out the additional apartments.