Considering Dante's trailer got smashed, it makes sense. The place is a complete wreck, it's not like he'd be living in the lap of luxury, he could fix it up and be able to operate out of it. It would also explain why the game introduced it as a location at all: Homeless dude discovers the inheritance that is his childhood home still standing and he, what, goes and rents a studio?
And it's not necessarily too big for him. One of my favorite shows had a small group of demon hunters living and working in a huge, run-down hotel after their original place got blown up. You take what you can get.