With zoning regulations largely instituted at the local level, NIMBY opposition tends to prevent high-density housing projects from being developed.

Maybe try to put some sort of a liability waiver, or some restriction on children playing outside unsupervised, in the lease which probably wouldn't prevent a lawsuit but would be better than nothing. 

How can I prevent this?

As an OOS owner, I don’t know how to (100%) prevent such things from happening.

Quote from @Brandon Allenczy: I try to prevent situations like this because they become revolving doors and you lose control over who resides there.The most I would do is add the new tenant for six months.

preventative maintenance, new a/c systems, new water heaters, raising rents Lessons learned?

@Tom Gimer, @Kevin SobiloIs there any way to prevent @Matt James' predicament in the future?

Estimate today's cost to replace that element (should be easy if new construction, more difficult to develop an accurate number for an older property, but absolutely do-able ), divide by number of years expected life, set aside that much each year until item is actually scheduled for replacement, adjusting the "remaining life" annually for accelerated deterioration or prolonged life due to well planned and executed preventative maintenance.

Definitely trim it to prevent damage, but the tree may provide value......?

Purchasing a property in the San Bernadino mountains.Will need a retaining wall built to prevent soil erosion.What sort of costs and planning should I expect with this type of project.