If you have events with fees, then you can set it up so that these fees are charged to the user's account right when they RSVP.
We'll talk about the first two parts here; instructions about the latter two can be found here.
Click the Manage badge, select "Settings" and "Edit Troop Settings" and scroll down to the bottom. You should see an option titled "Automatically charge event fees to scout accounts when they RSVP to an event with fees". Select this this option.
Next, you'll need to make sure your event has an attendance fee entered. Do this by going to the Edit Event page for that event, and in the Advanced tab you will find two fields: "Youth Fees" and "Adult fee." Enter the appropriate fees.
Starting when you activate the setting, when someone who is the owner of a money account RSVPs for an event with a fee, his or her account will be automatically charged, and the money will be transferred to the troop account. Nothing will happen for RSVPs entered before the setting is enabled. This means that enabling the setting will not upset your accounts with loads of new transactions. Nor will transactions made through this feature be removed if this setting is later disabled. If there are multiple troop accounts, then by default the troop account which is alphabetically first will be used--the same thing happens if the person RSVP-ing has multiple accounts; whichever one comes alphabetically first will be used. Also, notice that this only works for those who are Owners of an account--so youth need to be the Owners of an account for this to automatically charge them.