Well, LIZS - that was patronising! I am not on ML yet, and DP has a good job, he is a graduate but there were no graduate jobs in his field so he had to start from the bottom. He's progressing, slowly. But thanks for the tips 
I can't stop spending time with them, FGS, they are DP's brother and SIL.
pigsmummy I see you haven't read the thread properly.
sparechange
They don't have a buy-to-let. They never had a buy-to-let. They bought a house, over 10 years ago, paid it off in full, and now they rent it out. They have one mortgage, and it is on their current home.
I can't tell you the job. I can only tell you it is basically consultancy work, and very, very specialist, and for very top end business. It is essentially self-employed, and he has been 'in training' for the past 18 months, for which he was paid by the firm for whom he now is associated with, a basic salary. So it't not a 'pay jump' as such - he is now doing the actual job, and will be paid for the work he does. He says he will be paid around £20k for the average job, and can average 4 in a month.
It involved 4 years of uni, post grad and then further vocational study for the next few years. All of which was entirely funded by PIL. Entirely - to the tune of about £30k, they said.
No, BIL's wife does not work.