The Pros you mention should be reflected in the purchase price, which erodes its profitability, assuming you will pay a market price. If you can buy it way under market, then it will be more profitable…although this may raise eyebrows with your relatives. It is good that your Dad can perform repairs; hope he can also screen tenants, collect rents, perform other landlording chores.
The Cons you mention are very real, and a good start. I’d just plug into your calculations a healthy expense allowance since it is near the water–ask any beachfront landlord here in San Diego about maintenance. Also, are the tenants seasonal? If so, your vacancy rate should be investigated. Best might be to talk to other landlords in the area.
All in all, taking on a multi-unit rental should be viewed as a job. Most people going into it make over-optimistic assumptions about both expenses and rents. It seldom makes economic sense unless appreciation can be expected.
