Converting a basement into apartment

[Johnny Fullerton]

I just closed on my investment property a 3 family I was considering converting my basement into a 1 bedroom apartment, but was wondering if there was any rules and regulation, also I don't see a downfall in this theory only probably the up front costs, but the upside is it would increase my rental income and cash flow; I think the pros outweigh the cons. Any input is appreciated as I've been trying to do my diligence so I figured I'd throw it up here for more insight. Thanx