Vacation of property

Hi I am Sunil. I have taken a property on rent in 2007 for running a physiotherapy clinic. The owner of the clinic is another doctor of 66 yrs age and is batchelor. I was running that clinic since 8 yrs and as he is good friend of mine and there was no proper agreement done and no notary or the agreement was registered. Recently I have done renovation and so much was spended for renevotion. Moreover the property is on his girl friend name whom I haven't seen till to date. Even I am not sure whether the property was registered on his girlfriend name. Two days back the owner got expired due to cardiac arrest. Now I am worried. As that clinic is only source of living and I have spend lot of money in renovation. Following are my questions1. Can I hold that propery by paying timely tent to his girlfriend or his relatives 2. Do they have any authority to vacate me as there is no proper agreement since 8 yrs(electricity and municipal Bill paied by me)3. Can I buy that property. To whom should I approach (girl friend or relatives) Pls help me out..