Put a contingency in the contract that the house shall be vacant XXX number of days before closing. I personally would not close with a tenant in place. A disgruntled evicted tenant might possibly damage the house. With no lease in place, and even with a lease, you don't know if the tenant is amenable to moving. I also would want an empty house befiore closing so I can could do a very thorough walk through. I would make sure that this is the Seller's issue, not mine.

You really need a Realtor on your side to represent your best interests. I am saying this due to the multitude of variables involved in your situation. Protect yourself and get a Realtor, besides typically the buyers agent is paid throught the sellers cooperating broker commission...so the cost to you is usually zero. In many cases where renters are involved everything needs to be in writing to protect you, the sellers, the renters and everyone involved. If you feel more confident with an attorney go for it. But a I feel a Realtor would be the more sound solution as they will have your interests in mind above all other aspects. Good luck. I can certainly reccomend a Realtor in your area if you need help.