Rainwater storage in the garage?

We are planning the house and garage.
The garage will be a prefabricated garage from Kemmler.
I happened to come across the rainwater storage solution in the garage on Kemmler's homepage. Sounds good. Unfortunately too expensive (2,000).

I like the idea because an outdoor rain barrel is unsightly, not frost-proof, and we don’t have a water connection in the garage.

I am considering routing the garage's rainwater drain through the garage to install a rain barrel myself.

Does anyone have experience or suggestions?

What do you want to achieve? Is it important to have water in the garage? Refilling the windshield washer system? Why do you need water in freezing conditions? For the garden? Do you want a complete rainwater harvesting system? Or just to collect water for garden irrigation? And what exactly do you get from Kemmler for 2000 euros?

Water is to be used for garden irrigation, for cleaning (bicycles, cars, motorcycle, garden tools, etc.), paddling pools, etc. Would like a simple solution mainly for garden irrigation with a connection option for a hose (not a complete rainwater concept). 2000 EUR at Kenmler for an indoor rainwater pipe, 500 l barrel with water connection and hose connection, overflow into drain pipe.

Addition: The garage section has a door to the garden at the back and is not used for cars but as a garden shed (garden furniture, toys, etc.).

According to usage, you don't need water when it's freezing (unless you like cleaning your vehicles in frost). This means the tank can also be placed outside, the penetrations of the water pipes into the interior are unnecessary (I suspect that is the cost driver). I would also want these penetrations to be done professionally. If it's done sloppily and ends up leaking, then 2000 euros is nothing.

Just look in hardware store brochures to see what 500-liter tanks cost. How and whether you can make it "nice" outside is something only you can decide. Depending on the garden, 500 liters is tight, maybe better to invest some money in more volume, making it technically simpler (i.e., outside the garage).

Why not simply drill a well? No water shortage in summer and manageable costs. Could also be done in the garage itself.