If my father allowed a friend to stay in his home because he borrowed money, is there any legal way to get this person out of the house?

Owing somebody money does NOT mean you have to let that person stay in the home. If the person is paying rent to your father, he is a tenant; in that case, your father would have to evict  him through the courts, and could only evict him 1) for breach of the lease or nonpayment of rent; 2) on 30 days notice if there  is an oral lease or a written month-to-month leasee; or 3) at the end of a written lease term, if the lease is not renewed.

If the person is not paying your father, he is a guest, and your father may ask him to leave at any time. If he won't leave, he becomes a trespasser; your father should be able to call the police to help remove him. Again, the fact that your father may owe him money has no bearing on his right to stay in your father's home.

Note that your father only owes the person the sum borrowed plus any interest or fees which were agreed to at the time of the loan; this person may NOT simply decide to increase what your father owes.

One possibility: if the person needs a place to stay, can your father work out a deal with him whereby each week he stays, a certain amount (e.g. $50 or $100) is deducted from what your father owes him? He would pay "rent" by reducing your father's debt. If your father wants to and can work out such a deal, make sure it is in writing.