@Daniel Fang For this kind of deal (6-unit being considered commercial, buy from auction), it's better to get a business partner who has done similar thing unless you have done extensive research and know the whole process inside and out. Otherwise it will be very risky to you as 1) CRE values totally different from residential properties, financials, appraisal, etc; 2) property management also runs differently from one single residential rental; 3) auction buying has much more things involved than buying from regular market.
To get a loan, llc is necessary because it is commercial loan, lenders need to close to an entity. And it's also better for yourself, in case anything goes wrong, llc protect your personal asset.
Owner occupied 5+ unit is not an advantage unless you consider SBA loans. Because 5+ unit underwrites by rent income and expenses. If owner occupies one unit and not paying rent, the income decreases so as the value.