Hello and thanks for replying.
My wife is a UK citizen. I'm a non-EU citizen currently on student viza (just finished my PhD). We do rent privately. The rent is about £200 a month and the council tax is very low (it's a small wooden chalet). I can find out exact amount if necessary. We share the house with my wife's son. He is 21 year old and employed, so I doubt he'd count as a dependant. I am a part-time (subject to viza conditions) research assistant at University on £17000 a year. My contract, however, ends with expiry of my viza at the end of January, subject to extension if a new viza is granted. My wife is in full-time employment and her income is about £13000. We have no other children apart from my wife's son.
Many thanks!