It depends on a lot of different factors such as
1.Is the seller organized and has all related documents handy?
2. Is the buyer obtaining a loan for the business? If so it will take a lot longer.
3. Has the buyer already done his homework on the industry prior to submitting an offer?
4. How long is the due diligence period that is agreed upon by the seller and buyer?
5. Are additional negotiations needed to secure the current office space with the landlord?
It can take anywhere from 2 weeks to 6 months because there are so many variables.
A good source for what it takes to buy a business can be found on this blog:
Archives | BizQuest's Business for Sale Blog
BTW the blogger states that over 90% of buyers never pull the trigger on buying a business. Some buyers analyze a deal to death and just keep asking questions then someone else swoops in and buys the business.
I wouldn't put too much weight into your friend buying this business until money changes hands.