Facebook Group Moderator

Hi, I am running a small business in New Zealand selling campervans.
I have 3 Facebook groups regarding backpacking in New Zealand; each has 47k, 36k, and 26k people. I haven't managed them at all in the last 3 years.
I have selected 'all posts need to be approved', so not many posts in the last few years. The groups' condition is not looking good now.
I didn't have much time to manage it; approving posts, etc., cost me time, and I'd like to have them back live.
Honestly, my budget is limited; I don't want to spend too much on it,but if you're doing well, this could be long-term.

I'm running this group so that when people join, they will see our website, and I have put our ad at the top of the group, which might bring in some traffic.

I want some help to manage these groups, removing the rubbish posts etc. I don’t think you have to create content daily.
However, I would like to hear your thoughts, your proposal, and how much you charge.
Thanks

Here are the group links:
https://www.facebook.com/groups/BuyAndSellBackpackerCarsNZ/
https://www.facebook.com/groups/bpknz/
https://www.facebook.com/groups/backpackingnewzealand/
My business is :
www.backpackercar.co.nz

We could start with 7 days, then 30 days, then on a monthly basis.
But please check my groups first and let me know your thoughts.
Thanks