Tenants DO NOT want to leave Need Advice

Hello, I just purchased a rental property duplex through wholesaler. We gave the current tenants a notice that we need them the evacuate in 30 days. We are asking the current tenants to leave as the property is not in optimal condition we like to have our rentals and we would like to fix it up to increase value and rents. Current rents are at $900 each unit =1800 once we refinance to a mortgage the mortgage will be from 2400-2500 total. Market rent is $1400-1500 for each unit. They have been in the property 20+ years and do not want to leave. The predicament we are in is the property is not in the condition to charge that much for rent and we would also leave a lot of money in the deal once we refinance if we cannot get in there to fix it up. Any advice for the situation would be much appreciated!!!