One user at a time : In the instance where there are a number of people required to work on a spreadsheet, they can only access it when no-one else is working on it.
Using Excelville.com, there are no costs associated with selling spreadsheets and you don't need to build and manage a separate site, which works out pretty well. Whatever path you take, I wish you the best of luck. Leave a comment and let me know how things are going for you.
Once you design the type of budgeting spreadsheets you want to use, it will be easy to copy it for subsequent months or years. You can also use just one sheet and create tabs for each month.
Most spreadsheet applications have built in formulas and functions that will do the math for you so you don't have to. You can keep a running balance of your accounts and you can have each category totaled as well. You can keep it as simple or make it as sophisticated as you please.
excel budget templates
spreadsheet templates for tracking