If you want to collect a mandatory electricity deposit, cleaning fee, or any other type of additional charge when a new reservation is made, you can use required add-ons.
Setup
First, create a new add-on for the charge you want to mandate. Simply navigate to Settings > Add-ons, and click New Add-on. If the add-on you are adding is just a charge and not a physical product, choose the type Other.

Next, navigate to Settings > Units and select a unit you want to require the add-on for. Once on the unit page, select the Add-ons tab. Click New Required Add-on.

Select the desired add-on, and select the reservation type you want the add-on to be required for. You can select Ongoing to require the add-on only for long term reservations, or Standard to only require the add-on for short term reservations. Select All to require the add-on for all reservation types.
If you want to be more picky about which reservations the add-on will be required for, you can specify the reservation source, min/max reservation dates, and even reservation length as requirements for when to require the add-on. You can even indicate if the qty is editable and if it should reflect the qty of adults, children, or pets. This can be useful for a required pet fee you want to charge per pet.
Click Save to complete.
The add-on has now successfully been set up to be required for a particular unit and reservation type. If you would like to make this same change to other units, use the import/export functionality to quickly do so.
How it works
Now that you have the add-on required, if a customer makes a new reservation that qualifies for the required add-on, they will be notified of the required add-on.

The add-on will be included in the reservation summary but will not be able to remove it like other add-ons.
If you make a new reservation from the back end (Reservations > New Reservation), required add-ons will be automatically included on the new reservation as well. If you add a new unit to an existing reservation, required add-ons will once again be included.
When you visit the reservation detail, you will see the required add-ons. They can be removed if desired.

Charges are automatically created for the required addon. If the required add-on is removed or if the unit the add-on was required for is removed, the add-on and it's charges are removed as well (if the charges are unpaid).