I have a 40g hex and two 5g betta tanks. I use a Python type vac on the larger tank, and tap water in all 3.
Each gets a 30-50% water change about every 2 weeks. The canister filter on the 40g gets cleaned every few months. The little internal filters on the betta tanks pretty much never needs cleaning - maybe once a year.
Plant maintenance on the 40g is about once a year, other than pulling out some duckweed with each water change (slow growing plants, many glued to decor). The 5gs have java fern and anuibas on wood and rocks and never really need maintenance.
No ferts, no co2. My cleaning lady wipes down the outside of the tanks every 2 weeks.
I'd say total maintenance on all 3 tanks is maybe 2 hours a month at the most.
Edited to add - right now I have some juvi dwarf rainbows in a 6.6g tank - they'll stay there till they are too big to be eaten by the mollies in my main tank. I am changing their water twice a week.