How to tell if a job is real and legitimate
In the past I have searched for jobs online and I am aware how hard it is to distinguish between professional, non professional and students. I have written here a few tips and tricks when searching for castings online.
One thing I would suggest is that when you are looking at jobs online to apply for is ALWAYS look out for spelling errors, you will find that non professionals will often use slang terms and incorrect grammar. This is also common with students making films but they will always specify that it is a student film that they are making. You will find that with professionals the correct grammar and spelling, punctuation etc is always used when putting out a casting, and there will be no typos - it will be like reading from a book.
Sometimes I find that if someone gives their name as part of a crew or company it is always good to google it. You may find a link to the company's website, their IMDB, their LinkdIn or even a link here on casting call pro! I find that this is a good step to make as it gives you just that extra bit of information about who they are, making things a bit more personal (also in worst case scenarios this helps you discover if they are a scam agency or company.)
Also you will find that usually they will reference their company or production house - which I always google to make sure that it is legit, similar to how I google the persons name. It might seem nosy but it is in your best interest.
Now a quick point about modelling. In the past I have had messages from male photographers asking me to do glamour modelling, when I have stated that I am only 17 and not interested - they did not leave me alone. It is illegal for anyone under the age of 18 to have glamour/nude pictures published and it is illegal to even consent too it without parents permission. I would steer clear of glamour modelling unless you know the photographer well, you know that it is their profession, and you know that you will have hold over the pictures, otherwise when you do eventually make it big those images could come back out of the woodwork. Also if its not a professional photographer, chances are that the man who asks you for a 'paid bedroom shoot.' is in it for his own pleasure.
My final point and thing to look out for would be that professionals will ALWAYS state their rate of pay, whether that be £100 or Equity rates you will find that it is always listed.