New here; fun pool plans!

Hi! New to the pool forum, and I'm working in conjunction with a fish forum to work on my new pool. The original plan was to move my sharks (once they're much bigger) to an outdoor lagoon until I realized how expensive it is! So, I'm going to go with freshwater fish once I have a suitable space to build something. I also know I want an awesome pool once I have a big enough house (plans to move in a year and a few months), so I figured that my fish and my pool could be combined. Sort of. I have plans drawn up, I'll try and upload them, but here is my plan -

There will be a large pool, not sure on the exact dimensions but pretty large, and probably about 6 feet deep at the deepest. It will be an odd oval sort of shape, I'll have to upload pics like I said. On the right side of it, there will be an island that will surround the pond for the fish which will also be concrete. There will be a sump system for the pond on the island as well, this will all be much easier to understand once you see the pictures. So the ultimate plan is this:

A lazy river going around the entire thing, with one half going through an actual pool (not full or regular sized, a bit smaller since there is also the river) and the other half of the lazy river going around the concrete island with the pond inside. There will also be water features in here, a hot tub next to the pool and a waterfall on the backside where the lazy river is going around the island. I am wondering a few things:

-What is the lowest possible cost for building something like this? Keep in mind I have not finalized and plans for dimensions, but assuming the pond is 20 feet across and 50 feet long, so assume probably 75 feet wide at the widest, and maybe 75 feet long at the longest. Again, this will be WAY easier to understand once you can see some pictures, and I will try and draw a plan of this digitally as well. I am a DIY guy, I don't know about building my own pool but the pond will entirely be done by me - I'm more worried about the cost of the lazy river/pool than the pond. Is $100K a feasible budget for the entire thing? Is even lower possible?

-What is the upkeep of a lazy river like? I know the pool costs around $100 per month (at the high end), but what about the river?

Thank you all, and I am super excited to be here and to share my idea with you!