Most owners neglect to maximize the value potential of  their property because they don't have pertinent information about local market trends." 2nd sentence isn't actually a sentence so toss that..."

I am looking to get in to the real estate business to fulfill my desire to design spaces and help breathe new life into neglected homes.

Or that there may be specifics to your circumstance that make less than a year OK.Some of those factors which you have to look in the mirror and discuss are - actual length of time held, past history, current practice, documents like emails and discussions with your professionals, the reason for selling - like the need to change geography or an unsolicited offer to purchase, or a contract price that meets your stated long term appreciation goals.It's not a question of what is OK.  

What's one thing you'd do differently under those circumstances and what's one thing you'd definitely repeat? 

Typically note owners are able to offer something called a "deed-in-lieu" (DIL) of foreclosure that allows you to sign over the deed and walk away from the house and the remainder of the debt instead of losing it to a full foreclosure depending upon the circumstances.

Try to use the spreadsheet as a baseline to get started, then understand where all the numbers comes from and customize it for your circumstance.

I realize with one property its simple, but I want to have a system in place as my properties grow, so I don't become overwhelmed and disorganized, and end up neglecting things. 

If they neglect to reciprocate, then it might be time for new tenants.

I'm looking at a couple of 30 unit apartments that have been poorly managed and neglected for some years.

I'm thinking this won't help me either as special circumstances required for discharging liens generally, but just thought I'd mention.