If you go through the trouble of assessing an area for potential, keeping up with area developments, making decisions on properties based on present and future value, a good rental property is worth a hell of a lot of money for a lot of reasons to a reasonably smart local operator with a smart, well-run portfolio backing up his other, more speculative moves.

.), and how healthy is the HOA financially, ie: are they adequately funding reserves for capital improvements (roofs, paving, etc.) and are there any current special assessments?

All we can do is try to assess them the best we can.

We will assess our learning, any areas of improvements as well as celebrate the things that we did well in order to be prepared for the next purchase.This first deal will not make us wealthy, but it was very important to us to take the first step.

Any recommendations on how best to appeal tax assessment on a multifamily property in the state of MO.  

If say the average for duplex's and triplex's in similar age, location, etc are 35k/unit then that could be a very rough estimation of the 4plex you are looking at.Finally, for my location, I would look at the tax assessment and make sure I'm not paying way over that amount. 

You would also be able to leverage resources you have as an agent to help you invest such as mls access to show yourself houses, well vetted forms for leases etc, access to online databases of assessment info not available for free to the public.

Sounds great, but high HOA dues and special assessments concern me.

If it appears vacant that you can look in the windows (keep in mind this is technically trespassing and therefore not strictly legal) and see if you can assess any information about the condition of the interior.

My guess is their reserve is under-funded which means HOA fees could arise and/or special assessments could arise.I learned this the hard way...and not on a rental, my personal residence!