how many units did you have until you hired property management?

[Lee Cruz]

Ive been reading that i should be hiring a property manager right away, even for my first property. Reason being PMs have the resources for marketing, vacancy and day to day operations. Where if i was managing it, it would create more of a job that a passive investment. I think ill still go ahead and manage my first few. 

Which got me thinking, at about how many doors can one person handle until you need professional management help? 10? 20? 30?

Thanks!