Foundation degrees are very different animals from pre-registration nursing programmes. I'm not aware of anyone being paid a salary (unless in your case the police are offering sponsorships) to do a foundation degree. Foundation degrees in health and social care in our area cost about £8000 a year for two years. Pre-registration nursing costs a lot more than that but students are often sponsored by the NHS so get a small sponsorship salary while they are learning. Students for nursing who are on a bursary get paid a lot less, but are eligible, via student support, for certain benefits.
TBH, the institution offering a place to your stepson should be able to tell him about all this, they must have a student support unit, and the publicity material for the course should have laid all this out.