Land lording, for me, averages about 1 hour per month per property.
It lumps up though - most months you have 5 minutes of work (checking to make sure rent was deposited into the account... it was. Maybe 5 minutes calling the occasional plumber or whatever.). Then when someone moves out (say, once/year or so), you'll have 10 hours of work getting the property ready and showing it to new potential tenants. Then back to very little time needed.
So it "averages" to one hour/month, but it's really more like a median of 5 minutes per month or less, and a rare spike of 10 hours in a weekend. This is, of course, assuming you have a property in a decent area and screen properly so you get good tenants (no drama, evictions rare) and do a good job with upkeep of the property (so repairs are rare).
And, of course, you can outsource it to a property manager that you will have to manage, but now you're looking at much less time. You can even outsource the repairs (via calling repairmen) or make it even MORE hands off and get a home warranty so the tenants call that number directly for repairs.
Of course this doesn't touch on the time needed to find good properties. But people worrying about being a landlord and it taking a bunch of time is an overblown and, frankly, false fear, IMO. If you have the constitution for it, it's not bad at all.