Would you consider a prospective investment if vendor is unable or unwilling to provide a base case financial forecast? The rationale of the vendor is that the prospective purchaser should be familiar with the industry and will be able to provide its own outlook when reviewing the current business.
I would consider this a red flag and indicative of a lack of financial planning and management. It would make me spend more time on the Accounting and Financial due diligence and look for evidence of financial discipline and growth over multiple years.
It depends. Would it be the case that there are any alternative resources to assess the financial forecast? What is the quality of existing financial material that is made available to you?