I am no landlording expert, but I wonder if buying in the same building would have some drawbacks, akin to putting all your eggs in one basket. Say a special assessment came up for each unit... You now own two, and have to come up with +/- twice the cash. Or, they have to raise condo fees, because not enough money is being put into the reserve fund, for some upcoming planned maintenance?
Although, there would be some convenient things, such as being onsite to deal with emergencies.
I think you'll likely be asked for some more solid numbers as well, by the more experienced landlord and investment types here.