Christian was helpful from the day we booked - messaging us the best possible bus and Metro route to his apartment in the Marais. It's amazingly central - the Arts and Metiers Metro stop is one minute away; Republique and Sebastopol/Reamur also both close. Those connect to everywhere in Paris. One of Paris's most delectable markets, Marche des Enfants Rouges, is three minutes from Christian's place.

The apartment is darling. Tiny (with effective use of furniture to maximise the space) but perfect for a holiday - up two flights of stairs which look like they were built a couple of hundred years ago and narrow (so exactly like I imagined Paris would be), a quiet street in a busy and lively neighbourhood. Bedroom and kitchen in a studio arrangement (and you can use a curtain divider if you want to) and a good bathroom with shower, toilet and a washing machine (which has some funny habits but works perfectly)! Beds are very important and this one is terrific, firm, reasonably new and with comfy pillows. Christian provides fresh towels, sheets and teatowels (torchons) each week. Even though the kitchen is compact, it is certainly possible to cook meals - when we needed an extra kitchen knife and chopping board, Christian kindly provided them. There is an espresso maker and a French press as well as a good range of pots and pans. This makes it possible to make meals in the apartment - and we had breakfast there most days (more money to spend on lunch!). We also made the occasional dinner with cepes and truffles bought just around the corner (oh the food is so good).
The apartment is also very cosy - very important if you like travelling in the European winter.
Christian and his wife Ghislaine, who live on the floor below, are extremely kind and hospitable- they had restaurant suggestions both of which were terrific, in the neo-bistro style. Absinthe Cafe, which is the local, is also very reliable and Au Bascou around the corner (don't forget to eat the hare).
I really really recommend this place - it's exactly as described in a lovely neighbourhood at a reasonable cost. One of the best airbnbs in our experience.