The system recognises that work can totally dry up for self-employed people. For several years the only work I could get was on a casual self-employed basis (supervising traffic surveys). I could get several weeks work in a row and then nothing for several months. I always 'did things by the book' (including genuinely seeking more permanent employment while 'signed on') and 'signed off' while I was working but I never encountered any problems 'signing on' again following a period of self-employment.
If you (or your friend) are claiming purely contribution based JSA (or its Universal credit equivalent) you will need to have made sufficient NI contributions - presumably you paid your self employed NI.
If it's income based JSA then the allowance it will take account of any other household income.
There may also be complications in that some of your self employed pay will be deemed to include advanced holiday pay and it can sometimes be argued that some of your holidays could be taken (paid by yourself from holiday pay) during quiet times.
I think there is a now a 7 day wait before you can be entitled to benefits (and then you would have to wait a month for first payment) so the sooner you claim the better. Once you have claimed once it's then easier to resurrect your claim if you need to claim again.
Any contribution based JSA will count towards taxable earnings.
Good luck
many thanks to you both,trying to explain this to my OH,I may as well talk to the cat!I know signing on is not what anyone chooses & OH not been out of work proper for 30 years.
This may be a wee bit too late but Class 2 contributions do not count toward entitlement to contribution based JSA but means-tested income based JSA is a possibility and it's normally paid fortnightly, not monthly.