I have $55K in the stock market at the moment and plan to save (and grow) the remaining in the stock market until I have enough to pay off the entire mortgage. 

Your dilemma boils down to two priorities: maximizing your investment growth versus creating financial stability for your personal residence.

I recall reading in Forbes that major foundation fixes can add surprising value, becuase it addresses the single biggest fear buyers have.. a shaky structure.From my three decades in fix-and-flips, Ive noticed how important it is to have a team you trust.. from attorneys who know probate deals to realtors willing to drive for dollars with you, scouting hidden gems.

Maybe it's early stages of a growth market.

I wanted to gather some wisdom from local investors on what neighborhoods/zip codes likely have the highest growth/appreciation potential for the coming years.

If so, I am curious the thoughts and drives behind that, like, maybe really wanted exact answers to you so thought posting on your specifics was best approach? 

How would you make it grow the quickest?

Sacramento seems to have a lot of inventory and buildable land which will increase supply keeping rent growth slow. 

What about drive approaches, parking lots, site lights, landscape, irrigation, etc.? 

It is a platform with a large user based which will help drive more potential viewers to your listing.