The man had no friends or family to tie him down or cause trouble for him. So, he was free. However, he reminds himself of his own poverty, and poverty means that you are not as free as you would think.

Hello Motahareh, The normal phrase is "kith and kin". That's an old fashioned way of saying "friends and family". Kin means family and is still used in the phrase "next of kin" if doctor wants to know who is your closest relative. So in this quote, "neither kith nor kin" means he doesn't have anyone to help him or even talk to. When he says "eleven shillings and six pence", that's very little money. So he's being ironic when he seems to be happy saying "as free as air", but actually points out he's actually got no money.

دوست و آشنایی تو انگلیس نداشتم و خیلی احساس آزادی داشتم در حد درآمد روزانه یازده شیلینگ و شش پنی.

Pleasure