Is there a period of time where we see an emergence of "professional" landlords who do not employ their tenants in some way?

I often hear landlords discussed as if they are a relatively modern phenomenon - landlords here being understood as individuals who own properties (either standalone or connected units) that they rent or lease out to other individuals for cash.

Obviously there are historical examples like Lords who had serfs/villeins/peasants working and living on their land, or various work arrangements where room and board were included as part of (or the entirety of) compensation for employment, and the existence of things like company towns. But I think most people, when discussing landlords, understand these arrangements as not a direct historical correlation to what we see today. Mainly, these all seem to be distinguished by the fact that the renter was in some way employed by the landlord.

Are there other examples of history of people, or a class of people, who primarly made their income by renting out property to others who made their own income elsewhere? When did this system emerge (or re-emerge) historically?

As a side question, is there a history of folks who are "landlords on the side", like the common pratice of having a vacation home you rent out?

Thank you!