Could you please be a little clearer with what the questions actually are.  

When the owner is tired of doing the work.

Any number of owners - Day-1 of the property becoming non-owner occupied!

Money well spent considering that Real Estate boo-boos are expensive

When the owner is not capable, then hire help.

you already asked this question.....

Ryan Huggins - Thousand Oaks, CA nailed this one!

I answered your other question

When the help uses poor grammar?

A good property manager is worth their weight in gold.  -Kasey

Any and every rental property.

When the owners need assistance!

The recommendation will depend upon the goals and objectives of the property owner(s) as well as other criteria.

When the owner needs or prefers assistance.

Anytime.

Corey Christiansen An interesting question.

In Virginia if the property owner is renting out a property and lives out of state they are required to appoint an In State contact to handle the property (This however doesn't HAVE to be a property management company here)

If they are going to rent it out, they should have a property manager.

Corey Christiansen Property management is not mandatory. However, it does make life a lot easier for the landlord.

do it from day one

Whenever they want to have it managed for them.

When they are lacking the grammatical skills necessary to self manage.

Corey Christiansen - no written rules for that. When one can't manage oneself, one should hire a property manager.

It depends on the client's desire...

It takes certain skills to handle and manage properties and most owners don't have the skill or the inclination.

Like a sales agent( you do more than just putting a home on MLS)  a property manager knows the state laws and  does alot more than just collecting rent.

Right at the start.

Same question asked twice.