Can I use CESU without a social security number?

I haven’t registered as an auto-entrepreneur yet, as it appears that my top-up health cover (presently covered under my husband’s social security number) is at risk. I’ve been asked to give someone some saxophone lessons in the short term - she’s moving away in 6 weeks - so, as long as I teach at her house, I presume I can be paid by chèque emploi service universel (CESU)? Do I use my husband’s social security number for setting up the CESU contract? So far I’ve been dependent on him so I haven’t got one of my own. My student is actually my kinesi so she already has this number as it’s on my carte vitale.

Does my student pay me direct with a cheque emploi that I can bank? Is this gross or nett of social costs? I’m charging her an hourly rate + 10% for paid holidays, so will I be paying deductions from this later on? Presumably setting up the contract means that either I become registered with the CESU administering body, or I declare it on our 2010 tax return. If I continue to go down the CESU route rather than register as an AE, how much could I earn before losing my right to be covered under my husband’s number? Because of trips to UK it’s obvious I won’t yet be earning enough to pay for my own health cover.