Thanks for your question. I am Sam and I am one of the UK tax experts here on Just Answer.
Yes the rental income will be subject to tax and always has been - so what new laws do you make reference to? Are you referring to the fact that the interest element of the loan repayment (which in a buy to let arrangement is the whole element of the repayment) will no longer be an allowable expense?
Whether you can buy this property in your sons name will be something you will need to discuss with the lender - as I doubt they will agree a purcahse or a transfer as your son may not have any capital or income to quantify a loan.
I would suggest putting the property in just your husbands name (so the rental income is only subject to 20% tax rather than some of it at 40% due to your income level approaching 40%) but again it may be that the lender is not willing to entertain this due to his lower income level.
Other than that - a joint purcahse at best will be treated as 50:50 share each - as unless you can prove that your husband funded a greater share - (so in his sole name or an election with evidence to back up the fact he would own a larger share) then the only other consideration is put it in all three of your names and share a third of the rental income each
You son then would probably pay NIL tax as he has his full personal allowances available. Your husabnd just 20% on his share and you would pay a mix of 20% and 40% on your share.
OF course please note other expenses incurred on the rental of this property will remin eligable to offset against the rents - such as insurance, maintenance, repairs etc
Let me know if I can assist further