I have a Fluke T3 which I use for voltage detecting. Would have preferred the one with the amp clamp facility, but as freebies go, I,can't complain.
I have two of the Fluke non-contact (magic wands) voltage indicators. One I have had for ages which doesn't have an on/off button, and a new one with an on/off button. I found sometimes, the batteries went dead on the old one, as it would be flashing away in my bag.
I also have a Fluke 78 Automotive multimeter, which I find useful for more than automotive work.
Can measure temperature.
Whether a multimeter is necessary for commercial work, depends on the type of work you carry, or intend to carry out.
I don't believe one is necessary for installation work, and an MFT can be used for fault finding.
If your work involves machinery however, then yes one could be a necessity.