Purchase with or without tenants?

[Stephanie Minor]

I'm new to REI and have started looking into my options for a multi family home to rent out. What are people's thoughts on purchasing real estate that is already occupied by tenants? I can see a con being that the tenants may not be ideal. I could see a pro being that I wouldn't have to start marketing right after purchase. What about rehab/increasing value if there are existing tenants? Raising rent? For an example of one of the properties I've looked at, there are two professional tenants on the first floor, and a two bedroom on the second floor - both are month-to-month without leases.