This depends on how much time and effort you want to put into it. For example, if you matched bet 8-10 hours a day, 7 days a week, you would invariably end up with a lot more per month than if you only matched bet for 3 hours each Saturday.
Making over £500 a month wouldn’t require too much time, making £1,000+ would certainly require more time and work.
Check out my review of Outplayed or to give matched betting a try head over for the free trial.