Amazon, the most important thing ... Don't leave your head in the UK.
The second most important thing ... Don't leave your head in the UK.
You get the idea.
There are alot of convincing people who are perfectly able to charm you out of every penny you have, or who can do alot worse things besides.
Personally I'd recommend renting on your own then perhaps looking for a flatmate later on when you are more settled in. Get yourself a Numero de Identidade de Extranjero, and register youself with the council (empadronamiento). With these you will be able to register with a health centre... If you are going to move over, best to do it properly.
One last thing.... Don't trust anybody.