We have done the same in the past. No need to register anywhere too official, just get your petit licence from the douanes, and declare the income on your yearly tax return as a micro-bic. In the past you only had to inform the mairie if your commune was one of those that collected tourist tax, but now I understand every B&B is supposed to register with the mairie. I believe some tourist boards get a bit sniffy about listing you if you are not registered with the local Chambre de Commerce and/or Gites de France, but there is no compulsion to do either of these things. At least not unless your B&B becomes a flourishing business or something on which you rely for the major part of your income.
If you do table de hôte (i.e. evening meals) as well it can get very slightly more complicated; no doubt those who offer this service can fill you in.
Interesting note from Will ref.Tourist Office. We were registered with CdC and paid all the extras including our local Tourist Tax. Maire informed etc.etc. The Tourist Office refused to list us as our rooms were not inspected by GdF. We even had a letter from the Tourist Office in Paris saying they were obliged to list us, followed by a phone call from our Maire and they still wouldn't list us!!Fortuneately we were always busy due to passing trade but even better, have now retired from the scene. Each Dept seems to work on it's own rules.
Regards.
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