Sole Trader issue

I have been approached by a client who is at retirement age, and in poor health who has been running a successful cleaning business as a sole trader for 25 years or so....turnover at present between 65-75k per annum.  As his health condition is not getting any better he has suggested passing some of his more commercial clients on to his wife to run, she has also just became self employed, is there anything to stop him continuing to trade, although downsizing his workload as say ABC Cleaning and his wife taking on some of his clients as a separate sole trader as ABC Commercial Cleaning?

Any advice would be greatly appreciated.