Grammatically, they are correct. Whenever you are just starting a job, you want to say things in a positive way--otherwise it seems to your employers that you will not work unless you are watched over at all times--sort-of like what Hakro said.
When do I start?
What is the earliest I can come in?
When do most people go home around here? (It opens the conversation for your employer to tell you what the hours are.)
I don't know about other countries, but in the US, most jobs have a probation period--where they can fire you without cause. The person that hires you is usually also the person that interviewed you for the job. Yes, you should feel as if you are still interviewing for the job and be careful with language that would make you sound lazy! It is so very HARD to fire someone after they have made it through the probation period, that they will be carefully watching you making sure that you are right for their company while on probation. You do not need someone to even think that you might be lazy! Language is the only way that you can communicate! I might not go as far, however, as to ask keepsakes' question concerning how many extra hours I'm allowed to work!....
....Keep your nose clean and well-under the radar until the coast is clear, is my motto!