Proper use of a volt meter is not something that requires a person with a lot of training
Voltage drop percentage is not hard to compute if you did not sleep through high school math 101
Measure the no load voltage
Measure the voltage under load
Do the math
To check the drop to the home
Turn everything off - read the voltage at the panel
Turn everything on - read the voltage at the panel
Yes, this is out side of a home inspection but not beyond the skill level of someone who can use a volt meter
Remember that voltage drop % does not require one to load a circuit to its max rating – just the current of what it is used for
That is why a long run of #14 to the gate lights is not a problem.
If one wants to go the next step - go and compute the % of voltage drop on #14 or #12 wire per 200 feet (or 1000 if you want) at rated current.
Having a feel for what readings should be is a good thing - at least if you see something that does not look good you can get on the NACHI BB and ask the experts
Remember that when the gage of wire is computed for a job all this math is done by someone that knows ohms law E=IR
A good electrician can teach this subject in one day