Another possibility might be adding additional sources of income - renting out the common space/room in the office if you have one, to the tenants for birthday parties etc, vending machines, coin operated laundry, pet fees, pet non refundable pet deposits.  

Just closed on one today :)Creatively you can get many revenue streams, advertising on the exterior, coin operated laundry, vending machines.

So it would depend on your market: are there more people who make 120k a year who don't want to (or can't) buy a house or people who make $9/hr who can't buy a house.Another aspect is the ability to add value to an apartment complex from raising rent, adding coin-op laundry (debatable on the profitability), rental storage, soda/vending machines not to mention the natural appreciation.

Saying you will do it and then vending out and making a margin on that work seems wrong.It would have been good to know upfront or in the contract, is what seems to be the big take away. 

Your particular DM "effort" had not been presented previously,  but it's easy to see why it did not work out as others have pointed out.I'm sorry you way overpaid for your list, but most can tell you just one and done isn't going to produce much...what we're talking about is not much like a vending machine; more like farming.

A lot of people are making an additional $150-300/month on 1 to 5 other things, from vending machines to arcade games. 

No but ATM's and vending machines are pretty popular. 

We will build an 8 unit complex with covered parking and potentially a value add by building a side building with coin operated washer and dryer accompanied by a vending machine that's loaded with materials related to washing/drying clothes.

@Hilary GravesA quick google search pretty much consistently shows that NOI starts with Gross Operating Income that includes all revenues generated from the operation of the property i.e. rents, pet fees, vending machines, covered parking privileges, laundry revenues, etc.You mention standards :-) which may be a keyword here.

You're on BP asking about Vending Machines?