My play would be to buy it and offer it back to sale to either the association or one of the homes that it borders as it would extend or double the size of several back yards.

Notice to quit is served for any violation (unregistered auto, messy yard, etc.) 

Property is almost turnkey with some exterior differed maintenance and a couple water heaters.I'll spare the details and keep the numbers simple.Property without garage income.Units leased for $625 each ($2500)MGT 10% Vacancy 10% Repairs 10% Maintenance 5% =$875Expenses = Water, Sewer, Electric (common area), Yard = $300PITI= $780Monthly Cash flow $545 = 14-15% CoC+ garage income closer to 16-17% CoCHoping for a little appreciation to cover my closing costs and selling expenses down the road. 

I found that the hassle of investing in rentals even in my back yard is such that I sold them after they significantly appreciated. 

A big thing with townhomes vs single family homes is the maintenance of the yard and HOA fees. 

Armies of rusted junk in acres and acres of people's front yards, right off the highway. 

@Kalen MillsMy neighbors dog crapped in my front yard without my consent !!!

Maybe $50-100 a month to one tenant to do those things and clean up the yard or get a landscaper. 

The appraisal came back 139k as is. there .18 acre yard in the back with a detached garage.

You can tell them they aren't allowed to use it, but there's nothing in your lease or the law that says they can't own it and leave it in the yard as long as it's not damaging anything.Unfortunately, you would need evidence they are using it before you could take action.