Investment Loan vs Primary Residence Loan

I dont understand the difference between conventional bank financing for a primary residence or an investment loan. How do rates differ? Are there more costs with an investment loan? Is it okay to rent out a primary residence? I was preapproved for a loan at 5% down, up to 400k. Currently, I do not own any properties and my primary residence is living with relatives. I want to focus on multifamily units. I don't know if I am supposed to live in this property or not. If I don't have to live in the property I could also look at SFH, but I still want to focus on multifamily. I am not sure who to talk to about this and what is legit. My mortgage broker was telling me it would be okay to call whatever purchase I make my primary residence even if I don't plan to move in. Is that right?