There are no hotels available on the territory of an airport, however, due to remote accessibility from the airport to the city downtown (7 kilometers), that will be easy to find hotels that are just 15 minutes from the airport.
Among those hotels are Marriott Lisbon, the Holiday Inn Lisbon Continental the Hotel Tivoli Tejo, the Hotel Olissippo Oriente, the NH Campo Grande and Radisson SAS Hotel Lisboa.
The rates for the hotels vary and may be found on the website of the hotel, which you may also find below.
You can get to any of these hotels by metro or public transport, which departures from the airport every 10-15 minutes, or you may take a taxi, which will cost approximately 15 euros and 15 minutes to get to the Lisbon downtown.
