i am not sure i agree here............ (maybe not to specifically with a goal to profit from them... but as a point of principle)
to be clear our lad (7 now) at birth my parents filled a junior isa for him... my mrs parents put £100 a month into an account for him, and both my wife and i put £100 a month each into an account for him. This is to hopefully mean he can go to uni or get a vocational qualification without worrying about debt - OR alternatively put towards a deposit on a house or something.
my point is........ I dont think we could be accused of being tight on him, but that said, if he is still living with us once he is in his 20s and has a job, i think it is entirely reasonable for him to pay - albeit mate rates - for his upkeep and rent....... more so as a life lesson to get used to the real world. chances are if that does happen the money will ultimately go right back to him - i know my parents helped me hugely over the years............ i still had to pay for my keep however (not that much) when i finished uni and moved back in with them.