It sounds normal, that’s how I do it when I rent a room.

So when they move in they owe:

1. Deposit

2. First months rent in full, no matter the move in date

3. Last months deposit

But then the second month they get a discounted rate based on how many days into the previous month they moved in. But it’s just for that month.

Then when they move out, they get the deposit if owed, and then I return any last months rent if they don’t stay to the end.

So it’s like you paid for 2/14-3/14 already, but you still owe for 3/15-3/31, but that amount is due March 1st because that’s when the rest of March’s rent is due

It should be one time only of $250, and April 1st and all the rest of the months following you will only owe the full rent (650) on the first

The flange is one issue, the other is water pressure, they require higher pressure, and a water hammer arrestor is also highly recommended. And the pipes still have to come down somewhere. And most flush valves are still connected to the wall