Water in the foam is a huge problem with some of them. I got one for essentially free and that was about what it was worth by the time I put in the effort to make it work well.
Overall, I find anything but the sails are pretty easy to fix. You can patch the fiberglass on hull easily, the rudder and dagger board are easy enough to repair if you have a complete one as a template.
My problem is that my model had an expanding foam poured into the haul as both flotation and for structural support. It was totally waterlogged, the boat weighed almost twice what it was supposed to weigh. I grew up learning to sail on a nice sunfish provided by the school, it was light and as a young teen I could carry it by myself. I could NOT pick up the one I owned.
I ended up peeling the top off of the hull and cutting out 75% of the interior foam to cut the weight but still keep it ridged.
Around me a good, functional sunfish should sell for no more than $1K, and they can be had for a fraction of that if you are not in a rush to buy one.
I do like the larger Flying J type of boats, but they are hard in comparison to a sunfish. Much more tippy and you would need a trailer. You can easily throw a sunfish in the bed of a truck.