Why the math is favorable
If you live in one unit, the property is a primary residence. That unlocks lower down payment options and better pricing than a pure investment purchase, while the other units help carry the payment.
In many Pennsylvania towns with older housing stock, including parts of Lancaster and York, small multi unit buildings are genuinely available at entry level prices.
What to consider honestly
You are becoming a landlord and a neighbor at the same time. Screening, leases, repairs, and the occasional awkward conversation come with the arrangement.
Budget for vacancy from day one, and qualify on the assumption that the other unit sits empty for a stretch. If the payment only works when it is rented, the plan is fragile.