I looked at buying a business that had been running for a long time and everything had come out of it to finance an equally opulent life style. I took the 'books' to an accountant who laughed at me and said that they should be paying me to take it off their hands!
The business owner also demanded to 'help' me during my first year because they too, basically because they didn't want to 'let their baby go'.
Before you proceed any further, I suggest you take financial advice about the existing business and whether or not it will withstand the financial constraints that he is asking you to agree to. I know the professional accountants gave me this impartial advice free of charge, knowing that I may become a long term customer.
They also will not mind you saying 'my accountant has advised me...' if you ever have to confront or end the contract with the bully.
After the financial advice was given to me and the threat of being given advice that I may or may not have wanted I walked away from the potential disaster.
I don't regret that decision for one moment.
I now have my own business that cost me less than 1/3 of the asking price for their failing one and that is growing steadily at a rate that I can control. I am not having to fight someone else's reputation.
Best of luck!! Go with your gut feeling!