How much of rent to set aside for maintenance/ repair costs?

[Victor So]

Hello BP! I'm about to house hack my condo by renting out one of my rooms. After collecting rent, how much of it do you set aside for future maintenance and repair costs such as cap ex and how much of it do you keep? I'm sure the costs will vary depending on what type of property you have but is there a general rule of thumb you follow? Any advice would be appreciated! Victor