I have some friends who own a business and both work together on their computers out of their homes.
They would like to collaborate together on some documents, QuickBooks files, etc.
As they seem to be on board with the whole "only one of us works on the file at a time" concept it seems that a SharePoint site or source control would suit them best. But those are too expensive and too complicated, respectively.
Something like DropBox might work but I'm not seeing any good or easy way for DropBox to alert User #2 that User #1 has a hold of the document (since DropBox is really designed for a single user).
What would be an easy and affordable collaboration solution for a two person business with no IT department?