Big can of worms Wayne, with no definitive answer as it all depends on a number of factors.
1. You can't register as a farmer unless you have 10 or possibly 15 hectares, minimum.
2. You need to prove previous experience in farming. Your local Chambre d'Agriculture would be your first port of call to clarify whether you qualify or would need to attend training courses.
There used to be incentives for 'new' farmers under the age of 40.
3.The painful bits! As there is no such thing in France as a 'smallholder', you're either a farmer or not. If you're a farmer buying, selling, producing, or generally making (or attempting to) make a living, then you fall under the umbrella of MSA to whom you'll pay in the region of 3000 plus Euro a year in cotisations to qualify for health care and family benefits, pension, etc.
The amount you pay in will eventually be adjusted to your actual income around the third year of operation, but only after you've paid up front!
You'll need to talk with an accountant with a specialist knowledge.
If you're intention is simply to keep a few animals for the freezer for own use, then all you need is a cheptel number and follow the necessary guidance and local health regulations of the DDSV through your Vet.
Hope this helps, and good luck!