Because the tasks now become a little blurred we work on Time and Materials costs for such work.
Some people are comfortable with tools. You may own an excavator. Your son may be an electrician.
There are many different situations and varying degrees of DIY.
You want to put in your own ground loop but need us to supply you with a design.
You have a heat pump and need someone to install it for you.
You need a full system design in order to decide what tasks you can take on yourself.