So let's say I buy this beautiful split window and love driving this thing around.

My biggest apprehension is that this $36,000 down payment is going to cut pretty deep into my cash reserves (pulling this out of the stock market) and only leave me with about $15,000 for future ventures (without dipping into emergency fund/savings).Not sure what the right answer is here.

Define what skills you could bring to the table to help investors - will you drive for dollars, be a bird dog, do data crunching.

Point is a lot can drive the price up to that figure.  

The one minor issue I had is they insisted on a "drive by" appraisal where someone just looks at it from the outside, and that came back with a lower valuation than I thought... but you can request a real appraisal after that if you're sure the value is higher.

OUT OF THE WOODSA Nationwide Lumber Shortage is Driving Up the Cost of Homebuilding in DenverAt the outset of the pandemic, when most experts believed COVID-19 would annihilate the housing market (LOL), sawmills sought to get ahead of the downturn by reducing production—and who can blame them (see: Recession, Great)?

I have a rental property in East Texas, the plumber is over there every couple months cleaning roots out of the cast iron pipes.

Their family lives in the duplex and relies on them for "cheap" housing in a pretty expensive area.They're reluctant to sell because they don't want to leave their family behind.So, I had an idea on my drive back home...maybe some of you have had this idea too:I was thinking I could offer to pay the rent of the tenants for 6 months using proceeds from my assignment fee.

I agree with @Lydia T. these pre-foreclosure owners are not the most motivated, as a matter of fact, they don't realize how deep they are until the bailiff post the 24h notice on the door. 

Sounds like you will be deep in the hole every month.