Due diligence -- tenant occupied fourplex

[Brandon Payne]

I am searching for a 2-4 unit to move into as my first purchase. I found a fourplex for sale that is currently tenant occupied. So far I've only looked at vacant properties.

How does buying a tenant occupied residence change my due diligence activities? 

Should I ask the owner for copies of the leases of the current tenants?

They listed a yearly GOI and expenses, but I'd like to know how they calculated that and should ask.

What information would you want when buying a tenant occupied building? Do you have any other pointers about how a tenant occupied purchase would change the normal flow of buying a property?

And it seems odd to say "normal" as I haven't bought a property yet.