@gottoget
I was wondering whether I could offer useful advice which was particularly relevant, as I live in Central London and know people who work in a really wide variety of fields.
The stipulation about living in London is something I am aware of within areas such as trading, when people are working for firms with a considerable reputation, but that wouldn't tally with the concept of the job being poorly paid.
My concern for you would be how he would pay for accommodation in Central London if he is being paid very little.
Having said that, it's not uncommon for people starting out in a first job in certain quarters to be paid a relatively small amount. They are generally subsidised by their parents and are not dependent on their own income.
The question about the sphere in which he has been offered a job has a certain relevance; there are some fields which are extremely difficult to get a start in in London, advertising and television, for instance. If I knew of someone offered a starter job in advertising, I would try everything I could to make it happen for them, because it is so hard to get into.
If it is a very special job which he would never be able to find in his own local area, moving to London would be something to think about, but you would need to be totally sure that the job offer was bona fide and also be prepared to fund his accommodation for several months, which could mean quite an unexpected expenditure for you. I would look up the company on the Companies House database, just to be sure.
If it's something like working in a computer shop, I'm not sure I would pursue it.