I had a set of plywood prop tanks coated in boat 2 part epoxy paint, they worked fairly wel but developed leaks once they sat empty for a few months.
The pros are that they are well insulated the wood expands if they leak to close the leak. The cons were that they were no cheaper than buying an acrylic tank from advance acrylics of a glass tank from some of the cheaper companies.
I would probably not do it again, too heavy to move and zero resale value
You could also build a wood frame and use pond liner but once again it's really not much cheaper and cheap stuff can cost a lot of money if your livestock dies