If you need to borrow the money then you need to talk to a lender, or a few lenders first. It all comes down to their lending pratices and the requirement on multi-family properties.
I would not advise on becoming a landlord, especially if the tenant is 30 feet away, for a first time home buyer.
"The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
- Alexis de Toqueville, 1835