I've seen usual rates from recruitment agencies anywhere between $28-$35 per hour and there is work thats on EBA that pay mid $30s and have all sorts of entitlements including site, travel and crib allowances
I'd say work comes and goes, especially during winter thats when work tends to drop due to bad weather, short days, but won't hurt to do traffic control aswell to keep busy.
How long is a piece of string? Actually it's not all that complex, but it's variable - depending on the employer.
Spotters come under the Building and Construction General On-site Award 2010 (unless you're subject to an EBA). They're classified as CW/ECW 2 which is on par with duties such as Traffic Controller. In fact some TC companies have some of their crew with Spotters' tickets - and will charge out those services to clients & pay staff at the same rates.
If you look at the current award (effective from 1 July 2019) the hourly base rate for CW/ECW 2 is $23.82. Most spotters (and TCs) however are employed on a casual basis which takes the base hourly rate to $28.88 plus Super & CoInvest (if you work the requisite hours). There are many employers (especially labor hire firms) that pay at this base level.
At the other end of the scale if you're lucky enough to score a job with an employer subject to the CFMEU EBA, their standard hourly rate is currently $46.45 or $58.07 for casuals. It's noteworthy that Spotters are classified as CW3 under that EBA, whilst TCs are classified as CW1 or CW2 - depending on experience.
As an employer myself, it's a tough decision to price yourself in a competitive market. Most of my my clients are "small commercial" & they're often one-off or piece-meal jobs. You can't price yourself out of a job, but when you charge out at rates almost the same as the EBA then you can't be paying wages at the same rate either. A labor hire company typically charges their client double their wage rate. I've made a commercial decision to fit somewhere in the middle of the range (for wages). It means I'm left with a much smaller margin for all the other overheads, but it also means staff get much more than the base award rate, are happier & more loyal in the long-term and reliability improves. It's a trade-off & delicate balancing act, but not all employers will see it the same way.
You should be expecting AT LEAST the base award rate. If not, I suggest you decline the job. If you're not valued at the basic hourly level, it's likely you'll also get screwed in other ways. I know that can be tough if you're just starting out & trying to get some experience - but in the long term it helps no-one. Be wary also of some labor hire firms that send you on jobs spotting for plant that you're not ticketed for. But that's a whole different issue.