You should only have to sign a contract after an interview and discussion of your rights/what your job will entail. Are you sure he wasn't talking about future plans? Some advice: don't give them any bank account/debit card or other important personal details (besides those listed on your CV) until you have met them, filled out some forms and got the job. They won't need your card details until they need to pay you and if they ask for them straight away then something unprofessional is probably going on.
If it is legit and you do sign a contract then leaving before the end date is a breach of contract and could get you into trouble. They could refuse to pay you or mess you around in other ways and you'll lose them as a valuable reference for future work, listing them on your CV as experience would then become risky in case your next employer chooses to check up on you using it. Maybe if they are set on writing up a contract try to find out about their rules on 'giving notice'? Or explain to them that you're specifically looking for a summer job but would be willing to work lots of hours.
Gumtree can be a little dodgy sometimes so take care with how you continue. Is the company reputable/known? Have they discussed pay or tax? If it's cash in hand
be careful don't do it as it could get you into a lot of trouble and you won't be able to claim against them if they screw you over. Hope you get yourself sorted anyway
Last edited by Beige_Angel; 29-06-2012 at 20:32.