I fitted my RO and di unit inside my house. Its on a board not that big. Takes up hardly any room.
Ran pipe straight to garden water storage tanks by the side of the house. You can cover these in to protect from frost.
Pump straight to tank in van or if you are on a slope like me just let gravity do the job.
When you expand you can look at a shed set up.
Cuts out additional expense to start.
Just another idea.