After the HOA hired a construction team to investigate they saw that it has been going on for some time and has been entering underneath the hardwood floor over the cement(subflooring).

(utilities available, large enough to allow for any required setbacks, no soils issues, etc.) 

I am in the process in purchasing my first property and my real estate agent is strongly suggesting that I get a eviromental test done on the property and soil before we close.

Sometimes floors are uneven because the joists that support the floor underneath are rotted, so you have nothing supporting the load on that area.

I do a lot of foundation repairs, mostly due to poor soil conditions.

You can do this in List Source by going underneath the "Property" tab and filtering by "Equity Percentage".

I wouldn't purchase a property this way unless you were able to do soil testing to make sure the tank wasn't leaking.  

Plantings mature at different rates, and you can add new features each year.Test your soilThe soil is just as important as what’s going into it.

You occasionally run into foundation issues with hillside homes on raised foundations ... either the soil shifts over time or after a heavy rain, or the piers don't go down far enough to properly support or the foundation, or the wood posts above the foundation gets rotted or eaten away by termites.

Some plants also handle different soil types better/worse than others.