I do have the time to do a ton of research, but of the two links I clicked on (told you I didn't have  lot of time) this Pew report seemed interesting, it is four years old, so COVID has had an impact, but we can roll with it. 

Inquire about the impact on the properties from the most recent flooding in the area (Dec. 2015).

That will have an impact on your cash flow.  

However, like @Russell Brazil pointed out, there mostly likely is not another RE bubble around the corner and whatever bubble is out there will not have a dramatic impact on RE prices, at least nationally.

If so, what impacts do you think it will have over your long term profitability investing in markets with weaker demand and greater supply relative to that demand?

You could also check the National Association of Residential Property Managers NARPM.org This lists PM by state and area:Hiring a property manager is an important decision, and can be an asset for a property investor, but can also be a detriment if not chosen carefully and without some due diligence.

Very generally speaking, does the fact that another tennant would be sharing the property negatively impact the amount of rent  I can collect on the main 3/2 - if so how much?

Bill and Kim will never know the impact they’ve had on our lives.

It is inevitable that you will make some mistakes along the way, just be educated enough and monitor your risk to minimize the impact of those mistakes.

Ladders, impact bit set, led light bulbs, angle grinder, toilet.