Hi mummies, does anyone has any idea roughly how much it will be if I want to partition an additional room out? Im staying with my mother in law n brother in law n my hubby n I can only afford a 4rm flat, so I'll need to make an additional room coz I dont want my kids to sleep in same room as my mother in law

My hubby thinks it's gona be ex n he's quite against the idea so I'll need an estimation so that I can find my own means.. I already lost the dream of have g my own house I dont want my kids to be deprived of their deserved privacy.. Pls hlp!!