*Need Quick Advice* Concrete apron completely undermined

[stully05]

Need some quick advice:
Went to look at a house that is for sale. House was excellent, pool great. Peeked under the decking of the downhill side of the pool and saw some major erosion issues. On a fairly large area (50 linear foot) the concrete apron is completely exposed underneath. It does appear there are some angular metal supports that appear to be part of the frame of the pool itself, but the original dirt has washed away. The house itself is built on a pretty steep slope. The inground pool was installed around 2004. There is a wooden deck that completely surrounds the pool 360 degree. Uphill side I imagine it is sitting on dirt, downhill side it built up with 4x4's. I have no experience with inground pools, but I imagine you can't leave the concrete apron unsupported like that...? When walking around the pool, it does look to be in good shape, level, no cracks etc.
Is this a disaster waiting to happen? Does this need fixing and if so how? Should I run away? Most secure solution I can think of is to tear down decking on downhill side, build a retaining wall, backfill with significant drainage solutions, then rebuild decking. Seems like it wouldn't be hard to spend 100k on something like that.
My wife loves the house and we've been looking for years so she says yes, although I have reservations for something that would require so much to make right when we only get 3 months of pool use. (We live in Wisconsin).
I've got photos - just trying to figure out how to upload

[Teapot1]

Your solution of retaining wall etc sounds right, use self compacting backfill material.

[stully05]

Added some photos for reference


https://imageshack.com/a/ZhTW7/1