A couple of thoughts from a serial entrepreneur who has sold businesses:
Your friend is being asked to buy a business, with real estate. He needs to do his “due diligence” on all the business financials. This means his boss opens the books and your friend hires an accountant with expertise in business valuation to look at the financial history and current condition of the business, the real estate, as well as the sales deal overall. It doesn’t sound like your friend has done this—otherwise he’d have a good sense for whether the real estate portion made sense. Your friend should not proceed without due diligence on the whole deal.
I sold one of my businesses to a long time staff member, and we did it in stages, something like what is being proposed here. The reason we structured it that way: the business had many “moving parts” and it would have been a lot—maybe too much—for someone inexperienced in business ownership to take on all at once. The staged approach let the buyer take on the “weight” of full business ownership gradually. Today, six years after complete transition, the business is still extremely successful, the buyer loves what she does—and she credits the staged transition as a foundation for all that.