The reason I say this...Building a house as a GC is not hard at all once you have the process (I hired someone 3.5 months ago that didn’t know anything, and he’s currently running 10 houses that are on schedule, and homeowners are singing his praises)..  

Likely to hire a builder to look after it.I have no experience in this.

They hired our lawn care company to cut the lawn/shrubs.

As an investor, you cannot afford to hire a poor business operator.  

If I were to hire this out to a manager, would they actually be able to do a better job then me or would it be worse because they aren't as invested?

Once I was ready to go full time, I hired a mentor to set us up for success.  

Do you hire a real estate agent to rent it for you?

The property manager in place when we purchased, we thought we'd hire too until we read their owner's agreement.

That being said, they may not be doing it directly themselves, for example they may hire an agent who has access to some off-market listings as well as doing a general search on the MLS.

I like doing the lawn service myself because I’ll hire someone that will go by there the same day, each month or every other week and take care of it and it will always look nice and neat.