This is considered a 12 unit, garden style apartment.

I would think putting 10 houses on 1 acre and building a type of garden style community would be quite attractive and extremely profitable.

Your HOA will also take care of the grounds by hiring landscapers to cut the grass, maintain gardens, and trim bushes.What is the cost overlay on a property  HOA vs outside maintenance? 

The valve was attached to a 1 foot piece of PEX which went to an 90 degree elbow, then another foot of PEX that ended in a T with a 6" PEX stub on either side, each ending in a plug.We attached them each to a garden hose (around 40psi if I remember right), filled them to capacity, got as much air as possible out, then closed the valve to retain pressure.

Lots of room to add value.Building needs about $15,000 in repairs(safety margin included) but I am using $20,000 because the siding may need to be replaced before the Cap Ex Fund(using 10%) would accumulate enough to cover it.It had snow on the roof, but I could see moss on it from the little bit I could see.

My personal residence gardener I've had for 15 years said he would do it for free.

A garden hose and some acetone is all you need. 

One interesting figure was the operating costs for a standard garden apartment average $5000/year - which works out to 1/2 of $833.33/month.They mention the affect of student loan debt on increasing the amount of long-term renters.

Has anyone ever rehabbed or marketed their properties with low Voc paints, sustainably harvested wood or bamboo, cork or refurbished wood. energy saving appliances, air filters, fruit trees, water gardens, passive house.I'm thinking this is something I would like to do but of course it's all about economics and these green things usually cost more.

If it's just a parking lot common area for example, you get a local gardener to do a bi monthly clean up and have him send you the bill.