I recommend you look into Tenancy In Common.
https://andysirkin.com/tenancy-in-common-tic/
You could buy only what you know you need from your landlord, such as 1 unit of a 4plex, for 1/4 the price of the whole building plus fees and markup.
Cheapest way to buy real estate. And your landlord could keep all the common areas if he were to sell the 3 other units in the same way, thereby kinda having control of the property in small but meaningful ways.
I recommend you do a bit more homework on realestae investing vs tossing out a ? here because you are prime target to get screwed