Hi Dennana,
When he has been moved to UC he will need to supply the DWP with Fit Notes until he has the medical assessment which will determine if he is fit or unfit for work.
Before that he will have interviews with his Jobcentre Work Coach who should ask him if he is well enough to continue with his self employment. If he says yes then the Work Coach should determine how many hours per week he is well enough to work. If no, he will be expected to engage in " work preparation" activities which should take into account his health condition.
Hope this helps,
David
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
