Is it hard to get a tradesperson in Tauranga?
It can be — the region has grown faster than the trades in it, and the honest constraint is the calendar. Putting your timing in the request means a business that cannot make it says so up front instead of going quiet.
How is it priced?
Usually a rate for a set number of hours, plus travel and sometimes gear hire. Ask what happens if the night runs long, since overtime is charged and is easier to agree beforehand.
Can I choose the music?
Most will take a must-play and a do-not-play list and read the room in between, which is the part you are paying for. A DJ who will only play your list is not really being used.
Do they bring the sound system?
Usually, though some venues have their own and some have sound limits or curfews. Say the venue in your request, because it changes what is needed and what is allowed.
How far ahead should I book?
For a wedding or anything in December, months. Weekend dates go first, so give the date early and you will have more to choose from.