Under estimating maintenance costs is the biggest source of failure I see for new landlords.I myself am super aggressive with calculation of physical depreciation of the plant.

If the tenant keeps a place nice, plants flowers, or does good maintenance I try to acknowledge that.

Isn't that a hotbed of a General Motors plant?  

Also, my wife is an agent, so I'm trying to "plant the seed" that I can help even if they want to list with an agent. 

I'll be planting seeds all winter.

Don't let her know you know about the plant.

@Tom Kelly is correct - your biggest issue is humidity and spillage.In Colorado, a single person may grow up to 99 plants if they are a care giver and getting a care giver license is laughably easy.  

A land surveyor is needed to create a plat map, this will show the divided area, including details about the provision of utilities, sewage, a road network, etc.Last time I had a similar project, the city has a 30% land loss that requires to be "open", plant trees, roads, open spaces, community areas, play courts, etc.The key to this is government requirements, so I would say your local codes determine on how the land would be structured.

When I consider a 2 - 4 unit MF property with a centralized heating plant, I first determine the cost to switch to separate heating/cooling per unit.

Also, about any major projects near the neighborhood (ie, major structures being built, roads being torn up, and a sewer plant or jails being built, etc).