Eviction if no contract exists while I'm buying the property

[Ben S.]

I'm in the process of buying a duplex in Minnesota.  The lower unit is vacant but the upper unit has the owner's son in it and he is unable to find another place to rent and is currently paying less than half in rent that I plan to rent this unit for. 

My question is if this person in the upper unit doesn't have a lease with the current owners when I purchase the place do I have the right to remove him from the property right away if he doesn't cooperate?  Right now the sellers are saying I can't talk to him to figure out this person's plans before the sale in about 1 month.  So they are expecting me to purchase this place then after purchase I'm supposed to talk with the renter to figure out the situation.  But I'm worried that I may be purchasing a property with a problematic renter and want to know my options.