Hi, I'm new to this board and am interested in merchandising. I want to know how much I can expect to get for jobs (I know they can vary widely) and the hours needed to complete each job. Just looking to see if this is worthwhile. Not relying on this as sole income, just for additional money.

Based on my own limited experience. I seen jobs for 30min that paid a few bucks & $8 Hour but jobs have a time limit for completion. like 90 mins for example. It varies. depends on the job You may have to take pictures, inventory, reset. and I never got any additional money for doing the job right when I went over the time limit.

Merchandising can be a challenge to break into and it is not for everyone. That said the pay can vary depending on where you are located. Some areas will pay more in order to get reliable employees and/or to account for higher cost of living.
Lately I have seen jobs posted at $8/hr and jobs at $15/hr.
Some jobs are flat rate pay and others are hourly. For some companies you may be an employee and others an independent contractor.
If I am doing a reset and it takes longer I get paid for the time it takes. You can't leave a reset until it is done. For example I had one scheduled this week that was estimated at 5 hours each for 2 merchandisers. Well because of a store situation beyond our control this reset ended up at 9 hours each. Will we get paid our total time, YES.
This week as an example I had project work scheduled for 30 minutes and reset work scheduled for 8 hours. They both pay hourly. Next week I have a flat fee project that I do monthly for which I am an independent contractor. I work for multiple companies and each one pays a little differently.
Word of advice.............resets are not really for beginners you would not want your first assignment to be a reset! Coverage or continuity jobs do not come up that often and many times are not even advertised but instead are filled by word of mouth.
I believe the best work to start with is project work, especially if it is self assign that way you can take on as little or as much as you feel comfortable. The other option is to find a position working with greeting cards, magazines or books.