Do you own an older multifamily? What should I lookout for before purchasing?

I’d like tips on what I should look for in regards to the building, tenants, location (though I think it’s obvious that better location, better tenants?).

I’m going to be modelling different scenarios and an older multi family will be one of the scenarios that I model. I want to find something cash flow positive and will run the cost on maintenance but am generally nervous about an older building being a maintenance money pit.

Thanks in advance.